30. DSI Host (DSI) applied to STM32L4R9xx and STM32L4S9xx only

30.1 Introduction

Portions Copyright (c) Synopsys, Inc. All rights reserved. Used with permission.

The display serial interface (DSI) is part of a group of communication protocols defined by the MIPI ^® Alliance.

The MIPI ^® DSI Host controller is a digital core that implements all protocol functions defined in the MIPI ^® DSI specification. It provides an interface between the system and the MIPI ^® D-PHY, allowing the user to communicate with a DSI-compliant display.

30.2 Standard and references

• • MIPI ^® Alliance Specification for Display Serial interface (DSI)
  v1.1 - 22 November 2011
• • MIPI ^® Alliance Specification for Display Bus interface (DBI-2)
  v2.00 - 16 November 2005
• • MIPI ^® Alliance Specification for Display Command set (DCS)
  v1.1 - 22 November 2011
• • MIPI ^® Alliance Specification for Display Pixel interface (DPI-2)
  v2.00 - 15 September 2005
• • MIPI ^® Alliance Specification for Stereoscopic Display Formats (SDF)
  v1.0 - 22 November 2011
• • MIPI ^® Alliance Specification for D-PHY
  v1.1 - 7 November 2011

30.3 DSI Host main features

• • Compliant with MIPI ^® Alliance standards (see Section 30.2: Standard and references )
• • Interface with MIPI ^® D-PHY
• • Supports all commands defined in the MIPI ^® Alliance specification for DCS:
  • – Transmission of all command mode packets through the APB interface
  • – Transmission of commands in low-power and high-speed during video mode
• • Supports up to two D-PHY data lanes
• • Bidirectional communication and escape mode support through data lane 0
• • Supports non-continuous clock in D-PHY clock lane for additional power saving
• • Supports ultra low-power mode with PLL disabled
• • ECC and checksum capabilities
• • Support for end of transmission packet (EoTp)
• • Fault recovery schemes
• • Configurable selection of system interfaces:
  • – AMBA APB for control and optional support for generic and DCS commands
  • – Video mode interface through LTDC
  • – Adapted command mode interface through LTDC
  • – Independently programmable virtual channel ID in video mode, adapted command mode and APB slave
• • Video mode interfaces features:
  • – LTDC interface color coding mappings into 24-bit interface:
    • • 16-bit RGB, configurations 1, 2, and 3
    • • 18-bit RGB, configurations 1 and 2
    • • 24-bit RGB
  • – Programmable polarity of all LTDC interface signals
  • – Extended resolutions beyond the DPI standard maximum resolution of 800x480 pixels
  • – Maximum resolution is limited by available DSI physical link bandwidth:
    • • Number of lanes: 2
    • • Maximum speed per lane: 500 Mbit/s
    • • See examples in Section 30.4.3: Supported resolutions and frame rates
• • Adapted interface features:
  • – Support for sending large amounts of data through the memory_write_start (WMS) and memory_write_continue (WMC) DCS commands
  • – LTDC interface color coding mappings into 24-bit interface:
    • • 16-bit RGB, configurations 1, 2, and 3
    • • 18-bit RGB, configurations 1 and 2
    • • 24-bit RGB
• • Video mode pattern generator:
  • – Vertical and horizontal color bar generation without LTDC stimuli
  • – BER pattern without LTDC stimuli

30.4 DSI Host functional description

30.4.1 General description

The MIPI® DSI Host includes dedicated video interfaces internally connected to the LTDC and a generic APB interface that can be used to transmit information to the display. More in detail:

• • LTDC interface:
  • – Used to transmit information in video mode, in which the transfers from the host processor to the peripheral take the form of a real-time pixel stream (DPI).
  • – Through a customized mode, this interface can be used to transmit information in full bandwidth in the adapted command mode (DBI).
• • APB slave interface: allows the transmission of generic information in command mode, and follows a proprietary register interface. This interface can operate concurrently with either LTDC interface in either video mode or adapted command mode.
• • Video mode pattern generator: allows the transmission of horizontal/vertical color bar and D-PHY BER testing pattern without any kind of stimuli.

The block diagram is shown in Figure 203 .

Figure 203. DSI block diagram

30.4.2 DSI Host pins and internal signals

Table 199 and Table 200 list, respectively, the DSI pins (alternate functions) and the internal input/output signals.

Table 199. DSI pins

Table 199. DSI pins (continued)

Table 200. DSI internal input/output signals

30.4.3 Supported resolutions and frame rates

The DSI specification does not define supported standard resolutions or frame rates. Display resolution, blanking periods, synchronization events duration, frame rates, and pixel color depth play a fundamental role in the required bandwidth. In addition, other link related attributes can influence the ability of the link to support a DSI-specific device, namely display input buffering capabilities, video transmission mode (burst or non-burst), bus turn-around (BTA) time, concurrent command mode traffic in a video mode transmission, or display device specifics. All these variables make it difficult to define a standard procedure to estimate the minimum lane rate and the minimum number of lanes that support a specific display device.

The basic assumptions for estimates are:

• • clock lane frequency is 250 MHz, resulting in a bandwidth of 500 Mbit/s for each data lane
• • the display must be capable of buffering the pixel data at the speed at which it is delivered in the DSI link
• • no significant control traffic is present on the link when the pixel data is being transmitted.

30.4.4 System level architecture

Figure 204 shows the architecture of the DSI Host

Figure 204. DSI Host architecture

The different parts have the following functions:

• • The DSI Wrapper ensures the interfacing between the LTDC and the DSI Host kernel. It can adapt the color mode, the signal polarity and manages the tearing effect (TE) management for automatic frame buffer update in adapted command mode. The DSI Wrapper also control the DSI regulator, the DSI PLL and specific functions of the MIPI® D-PHY.
• • The LTDC interface captures the data and control signals from the LTDC and conveys them to a FIFO for video control signals and another one for the pixel data. This data is then used to build one of the following:
  • – Video packets, when in video mode (see Section 30.5 )
  • – The memory_write_start and memory_write_continue DCS commands, when in adapted command mode (see Section 30.6 )
• • The register bank is accessible through a standard AMBA-APB slave interface, providing access to the DSI Host registers for configuration and control. There is also a fully programmable interrupt generator to inform the system about certain events.
• • The PHY interface control is responsible for managing the D-PHY interface. It acknowledges the current operation and enables low-power transmission/reception or a high-speed transmission. It also performs data splitting between available D-PHY lanes for high-speed transmission.
• • The packet handler schedules the activities inside the link. It performs several functions based on the interfaces that are currently operational and the video transmission mode that is used (burst mode or non-burst mode with sync pulses or sync events). It builds

long or short packet generating correspondent ECC and CRC codes. This block also performs the following functions:

• – packet reception
• – validation of packet header by checking the ECC
• – header correction and notification for single-bit errors
• – termination of reception
• – multiple header error notification
• – depending on the virtual channel of the incoming packet, the handler routes the output data to the respective port.
• • The APB-to-generic block bridges the APB operations into FIFOs holding the generic commands. The block interfaces with the following FIFOs:
  • – Command FIFO
  • – Write payload FIFO
  • – Read payload FIFO
• • The error management notifies and monitors the error conditions on the DSI link. It controls the timers used to determine if a timeout condition occurred, performing an internal soft reset and triggering an interruption notification.

30.5 Functional description: video mode on LTDC interface

The LTDC interface captures the data and control signals and conveys them to the FIFO interfaces that transmit them to the DSI link.

Two different streams of data are present at the interface, namely video control signals and pixel data. Depending on the interface color coding, the pixel data is disposed differently throughout the LTDC bus.

Interface pixel color coding is summarized in Table 201 .

Table 201. Location of color components in the LTDC interface

The LTDC interface can be configured to increase flexibility and promote correct use of this interface for several systems. The following configuration options are available:

• • Polarity control: all the control signals are programmable to change the polarity depending on the LTDC configuration.
• • After the core reset, DSI Host waits for the first VSYNC active transition to start signal sampling, including pixel data, thus avoiding starting the transmission of the image data in the middle of a frame.
• • If interface pixel color coding is 18 bits and the 18-bit loosely packed stream is disabled, the number of pixels programmed in the VPSIZE field must be a multiple of four. This means that in this mode, the two LSBs in the configuration are always inferred as zero. The specification states that in this mode, the pixel line size must be a multiple of four.
• • To avoid FIFO underflows and overflows, the configured number of pixels is assumed to be received from the LTDC at all times.
• • To keep the memory organized with respect to the packet scheduling, the number of pixels per packet parameter is used to separate the memory space of different video packets.

For SHTDN and COLM sampling and transmission, the video streaming from the LTDC must be active. This means that if the LTDC is not actively generating the video signals like VSYNC and HSYNC, these signals are not transmitted through the DSI link. Because of such constraints and for commands to be correctly transmitted, the first VSYNC active pulse must occur for the command sampling and transmission. When shutting down the display, it is necessary for the LTDC to be kept active for one frame after the command being issued. This ensures that the commands are correctly transmitted before actually disabling the video generation at the LTDC interface.

The SHTDN and COLM values can be programmed in the DSI Wrapper control register (DSI_WCR).

For all of the data types, one entire pixel is received per each clock cycle. The number of pixels of payload is restricted to a multiple of a value, as shown in Table 202 .

Table 202. Multiplicity of the payload size in pixels for each data type

30.5.1 Video transmission mode

There are different video transmission modes, namely:

• • Burst mode
• • Non-burst mode
  • – Non-burst mode with sync pulse
  • – Non-burst mode with sync event

Burst mode

In this mode, the entire active pixel line is buffered into a FIFO and transmitted in a single packet with no interruptions. This transmission mode requires that the DPI pixel FIFO has the capacity to store a full line of active pixel data inside it. This mode is optimally used when the difference between the pixel required bandwidth and DSI link bandwidth is significant, it enables the DSI Host to quickly dispatch the entire active video line in a single burst of data and then return to low-power mode.

Non-burst mode

In this mode, the processor uses the partitioning properties of the DSI Host to divide the video line transmission into several DSI packets. This is done to match the pixel required bandwidth with the DSI link bandwidth. With this mode, the controller configuration does not require a full line of pixel data to be stored inside the LTDC interface pixel FIFO. It requires only the content of one video packet.

Guidelines for selecting the burst or non-burst mode

Selecting the burst and non-burst mode is mainly dependent on the system configuration and the device requirements. Choose the video transmission mode that suits the application scenario. The burst mode is more beneficial because it increases the probability of the link spending more time in the low-power mode, decreasing power consumption. The following conditions must be met to get the maximum benefits from the burst mode of operation:

• • The DSI Host core must have sufficient pixel memory to store an entire pixel line to avoid the overflow of the internal FIFOs.
• • The display device must support receiving a full pixel line in a single packet burst to avoid the overflow on the reception buffer.
• • The DSI output bandwidth must be higher than the LTDC interface input bandwidth in a relation that enables the link to go to low-power once per line.

If the system cannot meet these requirements, it is likely that the pixel data is lost causing the malfunctioning of the display device while using the burst mode. These errors are related to the capabilities of the system to store the temporary pixel data.

If all the conditions for using the burst mode cannot be met, use the non-burst mode to avoid errors. The non-burst mode provides a better matching of rates for pixel transmission, enabling:

• • Only a certain amount of pixels to be stored in the memory and not requiring a full pixel line (lesser LTDC interface RAM requirements in the DSI Host).
• • Operation with devices that support only a small amount of pixel buffering (less than a full pixel line).

The DSI non-burst mode must be configured so that the DSI output pixel ratio matches with the LTDC interface input pixel ratio, reducing the memory requirements on both host and/or device side. This is achieved by dividing a pixel line into several chunks of pixels and optionally interleaving them with null packets.

The following equations show how the DSI Host core transmission parameters must be programmed in non-burst mode to match the DSI link pixel output ratio (left hand side of the “=” sign) and LTDC interface pixel input (right hand side of the “=” sign).

When the null packets are enabled:

When the null packets are disabled:

30.5.2 Updating the LTDC interface configuration in video mode

It is possible to update the LTDC interface configuration on the fly without impacting the current frame. It is done with the help of shadow registers. This feature is controlled by the DSI Host video shadow control register (DSI_VSCR).

The new configuration is only used when the system requests for it. To update the video configuration during the transmission of a video frame, the configuration of that frame needs to be stored in the auxiliary registers. This way, the new frame configurations can be set through the APB interface without corrupting the current frame.

By default, this feature is disabled. To enable this feature, set the enable (EN) bit of the DSI Host video shadow control register (DSI_VSCR) to 1.

When this feature is enabled, the system supplies the configuration stored in the auxiliary registers.

Figure 205 shows the necessary steps to update the LTDC interface configuration.

Figure 205. Flow to update the LTDC interface configuration using shadow registers

graph TD
    A[Configure the LTDC interface] --> B[Request update]
    B --> C[Read DSI Host LTDC shadow control register]
    C --> D{UR}
    D -- Active --> C
    D -- Accepted --> E[Start video engine]
    E --> F[New resolution]
    F --> A
  

Immediate update

When the shadow register feature is active, the auxiliary registers requires the LTDC configuration before the video engine starts. This means that, after a reset, update register (UR) bit is immediately granted.

When it is required to immediately update the active registers without the reset (as in Figure 206 ), ensure that the enable (EN) and update register (UR) bits of the DSI Host video shadow control register (DSI_VSCR) are set to 0.

Figure 206. Immediate update procedure

Updating the configuration during the transmission of a frame using APB

To update the LTDC interface configuration, follow the steps shown in Figure 207 :

1. 1. Ensure that the enable (EN) bit of the DSI Host video shadow control register (DSI_VSCR) register is set to 1.
2. 2. Set the update register (UR) bit of DSI Host video shadow control register (DSI_VSCR) to 1.
3. 3. Monitor the update register (UR) bit. This bit is set to 0 when the update is complete.

Figure 207. Configuration update during the transmission of a frame

Requesting a configuration update

It is possible to request for the LTDC interface configuration update at any part of the frame. DSI Host waits until the end of the frame to change the configuration. However, avoid sending the update request during the first line of the frame because the data must propagate between clock domains.

30.6 Functional description: adapted command mode on LTDC interface

The adapted command mode, enables the system to input a stream of pixel from the LTDC that is conveyed by DSI Host using the command mode transmission (using the DCS packets). The adapted command mode also supports pixel input control rate signaling and tearing effect report mechanism.

The adapted command mode makes it possible to send large amounts of data through the memory_write_start (WMS) and memory_write_continue (WMC) DCS commands. It helps in delivering a wider data bandwidth for the memory write operations sent in command mode to MIPI® displays and to refresh large areas of pixels in high resolution displays. If additional commands such as display configuration commands, read back commands, and tearing effect initialization are to be transferred, then the APB slave generic interface must be used to complement the adapted command mode functionality.

Adapted command mode of operation supports 16 bpp, 18 bpp, and 24 bpp RGB.

To transmit the image data in adapted command mode:

• • Set command mode (CMDM) bit of the DSI Host mode configuration register (DSI_MCR) to 1.
• • Set DSI mode (DSIM) bit in the DSI Wrapper configuration register (DSI_WCFGR) to 1.

To transmit the image data, follow these steps:

• • Define the image area to be refreshed, by using the set_column_address and set_page_address DCS commands. The image area needs to be defined only once and remains effective until different values are defined.
• • Define the pixel color coding to be used by using the color coding (COLC) field in the DSI Host LTDC color coding register (DSI_LCOLCR).
• • Define the virtual channel ID of the LTDC interface generated packets using the virtual channel ID (VCID) field in the DSI Host LTDC VCID register (DSI_LVCIDR). These also need to be defined only once.
• • Start transmitting the data from the LTDC setting the LTDC enable (LTDCEN) bit of the DSI_WCR register.

Figure 208 shows the adapted command mode usage flow.

Figure 208. Adapted command mode usage flow

sequenceDiagram
    participant VE as Video engine
    participant DC as DSI controller
    participant D as Display
    Note left of VE: 
    VE->>DC: genIF: set_column_address
    DC->>D: DCS: set_column_address
    Note left of VE: 
    VE->>DC: genIF: set_page_address
    DC->>D: DCS: set_page_address
    Note left of VE: 
    VE->>DC: LTDCIF: vsync = 1, dpidataen = 1
    DC->>D: DCS: write_memory_start
    Note left of VE: 
    VE->>DC: LTDCIF: vsync = 0, dpidataen = 0
    DC->>D: DCS: write_memory_continue1
    DC->>D: DCS: write_memory_continue2
    DC->>D: DCS: write_memory_continue3
    Note right of D: MSv35860V1
  

When the command mode (CMDM) bit of the DSI Host mode configuration register (DSI_CFGR) is set to 1, the LTDC interface assume the behavior corresponding to the adapted command mode.

In this mode, the host processor can use the LTDC interface to transmit a continuous stream of pixels to be written in the local frame buffer of the peripheral. It uses a pixel input bus to receive the pixels and controls the flow automatically to limit the stream of continuous pixels. When the first pixel is received, the current value of the command size (CMDSIZE) field of the DSI Host LTDC command configuration register (DSI_LCCR), is shadowed to the internal interface function. The interface increments a counter on every valid pixel that is input through the interface. When this pixel counter reaches command size (CMDSIZE), a command is written into the command FIFO and the packet is ready to be transmitted through the DSI link.

If the last pixel arrives before the counter reaches the value of shadowed command size (CMDSIZE), a WMS command is issued to the command FIFO with word count (WC) set to the amount of bytes corresponding to the value of the counter. If more than CMDSIZE pixels are received (shadowed value), a WMS command is sent to the command FIFO with WC set to the number of bytes corresponding to the command size (CMDSIZE) and the counter is restarted.

After the first WMS command has been written to the FIFO, the circuit behaves in a similar way, but issues WMC commands instead of WMS commands. The process is repeated until the last pixel of the image is received. The core automatically starts sending a new packet

when the last pixel of the image is received, falls or command size (CMDSIZE) limit is reached.

Synchronization with the LTDC

The DSI Wrapper performs the synchronization of the transfer process by:

• • controlling the start/halt of the LTDC
• • making the data flow control between LTDC and DSI Host.

The transfer to refresh the display frame buffer can be triggered

• • manually, setting the LTDC enable (LTDCEN) bit of the DSI Wrapper control register (DSI_WCR)
• • automatically when a tearing effect (TEIF) event occurs and automatic refresh (AR) is enabled.

The selection between manual and automatic mode is done through the automatic refresh (AR) bit of the DSI Wrapper configuration register (DSI_WCFGR).

Once the transfer of one frame is done whatever in manual or automatic refresh mode, the DSI Wrapper is halting the TFT display controller (LTDC) resetting the LTDC enable (LTDCEN) bit of the DSI Wrapper control register (DSI_WCR) and set the end of refresh interrupt flag (ERIF) flag of the DSI Wrapper status register (DSI_WSR). If the end of refresh interrupt enable (ERIE) bit of the DSI Wrapper configuration register (DSI_WCFGR) is set, an interrupt is generated.

The end of refresh interrupt flag (ERIF) flag of the DSI Wrapper status register (DSI_WSR) can be reset setting the clear end of refresh interrupt flag (CERIF) bit of the DSI Wrapper clear interrupt flag register (DSI_WCIFR).

The halting of the TFT display controller (LTDC) by the DSI Wrapper is done synchronously on a rising edge or a falling edge of VSync according to the VSync polarity (VSPOL) bit of the DSI Wrapper configuration register (DSI_WCFGR).

Support of tearing effect

The DSI specification supports tearing effect function in command mode displays. It enables the Host processor to receive timing accurate information about where the display peripheral is in the process of reading the content of its frame buffer.

The tearing effect can be managed through

• • a separate pin, which is not covered in the DSI specification
• • the DSI tearing effect functionality: a set_tear_on DCS command must be issued through the APB interface using the generic interface registers.

Tearing effect through a GPIO

When the tearing effect source (TESRC) bit of the DSI Wrapper configuration register (DSI_WCFGR) is set, the tearing effect is signaled through a GPIO.

The polarity of the input signal can be configured by the tearing effect polarity (TEPOL) bit of the DSI Wrapper configuration register (DSI_WCFGR).

When the programmed edge is detected, the tearing effect interrupt flag (TEIF) bit of the DSI Wrapper interrupt and status register (DSI_WISR) is set.

If the tearing effect interrupt enable (TEIE) bit of the DSI Wrapper interrupt enable register (DSI_WIER) is set, an interrupt is generated.

Tearing effect through DSI link

When the TESRC bit of the DSI Wrapper configuration register (DSI_WCFGR) is reset, the tearing effect is managed through the DSI link:

The DSI Host performs a double bus turn-around (BTA) after sending the set_tear_on command granting the ownership of the link to the DSI display. The display holds the ownership of the bus until the tear event occurs, which is indicated to the DSI Host by a D-PHY trigger event. The DSI Host then decodes the trigger and reports the event setting the tearing effect interrupt flag (TEIF) bit of the DSI Wrapper interrupt and status register (DSI_WISR).

If the tearing effect interrupt enable (TEIE) bit of the DSI Wrapper interrupt enable register (DSI_WIER) is set, an interrupt is generated.

To use this function, it is necessary to issue a set_tear_on command after the update of the display using the WMS and WMC DCS commands. This procedure halts the DSI link until the display is ready to receive a new frame update.

The DSI Host does not automatically generate the tearing effect request (double BTA) after a WMS/WMC sequence for flexibility purposes, so several regions of the display can be updated improving DSI bandwidth usage. Tearing effect request must always be triggered by a set_tear_on command in the DSI Host implementation.

Configure the following registers to activate the tearing effect:

• • DSI Host command mode configuration register (DSI_CMCR): TEARE
• • DSI Host protocol configuration register (DSI_PCR): BTAE.

30.7 Functional description: APB slave generic interface

The APB slave interface allows the transmission of generic information in command mode, and follows a proprietary register interface. Commands sent through this interface are not constrained to comply with the DCS specification, and can include generic commands described in the DSI specification as manufacturer-specific.

The DSI Host supports the transmission of write and read command mode packets as described in the DSI specification. These packets are built using the APB register access. The DSI Host generic payload data register (DSI_GPDR) has two distinct functions based on the operation. Writing to this register sends the data as payload when sending a command mode packet. Reading this register returns the payload of a read back operation. The DSI Host generic header configuration register (DSI_GHCR) contains the command mode packet header type and header data. Writing to this register triggers the transmission of the packet implying that for a long command mode packet, the packet payload needs to be written in advance in the DSI Host generic payload data register (DSI_GPDR).

The valid packets that can be transmitted through the generic interface are the following:

• • Generic write short packet 0 parameters
• • Generic write short packet 1 parameters
• • Generic write short packet 2 parameters
• • Generic read short packet 0 parameters
• • Generic read short packet 1 parameters
• • Generic read short packet 2 parameters
• • Maximum read packet configuration
• • Generic long write packet
• • DCS write short packet 0 parameters
• • DCS write short packet 1 parameters
• • DCS read short packet 0 parameters
• • DCS write long packet.

A set of bits in the DSI Host generic packet status register (DSI_GPSR) reports the status of the FIFO associated with APB interface support.

Generic interface packets are always transported using one of the DSI transmission modes, i.e. video mode or command mode. If neither of these modes is selected, the packets are not transmitted through the link and the related FIFO eventually becomes overflowed.

30.7.1 Packet transmission using the generic interface

The transfer of packets through the APB bus is based on the following conditions:

• • The APB protocol defines that the write and read procedure takes two clock cycles each to be executed. This means that the maximum input data rate through the APB interface is always half the speed of the APB clock.
• • The data input bus has a maximum width of 32 bits. This allows for a relation to be defined between the input APB clock frequency and the maximum bit rate achievable by the APB interface.
• • The DSI link pixel bit rate when using solely APB is \( (\text{APB clock frequency}) * 16 \) Mbit/s.
• • When using only the APB interface, the theoretical DSI link maximum bit rate can be expressed as \( \text{DSI link maximum bit rate} = \text{APB clock frequency (in MHz)} * 32 / 2 \) Mbit/s.

In this formula, the number 32 represents the APB data bus width, and the division by two is present because each APB write procedure takes two clock cycles to be executed.

• • The bandwidth is dependent on the APB clock frequency; the available bandwidth increases with the clock frequency.

To drive the APB interface to achieve high bandwidth command mode traffic transported by the DSI link, the DSI Host must operate in the command mode only and the APB interface must be the only data source that is currently in use. Thus, the APB interface has the entire bandwidth of the DSI link and does not share it with any another input interface source.

The memory write commands require maximum throughput from the APB interface, because they contain the most amount of data conveyed by the DSI link. While writing the packet information, first write the payload of a given packet into the payload FIFO using the DSI Host generic payload data register (DSI_GPCR). When the payload data is for the command parameters, place the first byte to be transmitted in the least significant byte position of the APB data bus.

After writing the payload, write the packet header into the command FIFO. For more information about the packet header organization on the 32-bit APB data bus, so that it is correctly stored inside the command FIFO.

When the payload data is for a memory write command, it contains pixel information and it must follow the pixel to byte conversion organization referred in the Annexe A of the DCS specification.

Figures 209 to 213 show how the pixel data must be organized in the APB data write bus.

The memory write commands are conveyed in DCS long packets, encapsulated in a DSI packet. The DSI specifies that the DCS command must be present in the first payload byte of the packet. This is also included in the diagrams. In figures 209 to 213, the write memory command can be replaced by the DCS command write memory Start and write memory Continue .

Figure 209. 24 bpp APB pixel to byte organization

Figure 210. 18 bpp APB pixel to byte organization

Figure 211. 16 bpp APB pixel to byte organization

Figure 212. 12 bpp APB pixel to byte organization

Figure 213. 8 bpp APB pixel to byte organization

30.8 Functional description: timeout counters

The DSI Host includes counters to manage timeout during the various communication phases. The duration of each timeout can be configured by the six timeout counter configuration registers (DSI_TCCR0...5).

There are two types of counters:

• • contention error detection timeout counters ( Section 30.8.1 )
• • peripheral response timeout counters ( Section 30.8.2 ).

30.8.1 Contention error detection timeout counters

The DSI Host implements a set of counters and conditions to notify the errors. It features a set of registers to control the timers used to determine if a timeout has occurred, and also contains a set of interruption status registers that are cleared upon a read operation (detailed in Table 203 ). Optionally, these registers also trigger an interrupt signal that can be used by the system to be activated when an error occurs within the DSI connection.

Table 203. Contention detection timeout counters configuration

Time units for these 16-bit counters are configured in cycles defined in the timeout clock division (TOCKDIV) field in the DSI Host clock control register (DSI_CCR).

The value written to the timeout clock division (TOCKDIV) field in the DSI Host clock control register (DSI_CCR) defines the time unit for the timeout limits using the lane byte clock as input.

This mechanism increases the range to define these limits.

High-speed transmission contention detection

The timeout duration is configured in the high-speed transmission timeout count (HSTX_TOCNT) field of the DSI Host timeout counter configuration register 1 (DSI_TCCR0). A 16-bit counter measures the time during which the high-speed mode is active.

If that counter reaches the value defined by the high-speed transmission timeout count (HSTX_TOCNT) field of the DSI Host timeout counter configuration register 1 (DSI_TCCR0), the timeout high-speed transmission (TOHSTX) bit in the DSI Host interrupt and status register 1 (DSI_ISR1) is asserted and an internal soft reset is generated to the DSI Host.

If the timeout high-speed transmission interrupt enable (TOHSTXIE) bit of the DSI Host interrupt enable register 1 (DSI_IER1) is set, an interrupt is generated.

Low-power reception contention detection

The timeout is configured in the low-power reception timeout counter (LPRX_TOCNT) field of the DSI Host timeout counter configuration register 1 (DSI_TCCR1). A 16-bit counter measures the time during which the low-power reception is active.

If that counter reaches the value defined by the low-power reception timeout counter (LPRX_TOCNT) field of the DSI Host timeout counter configuration register 1 (DSI_TCCR0), the timeout low-power reception (TOLPRX) bit in the DSI Host interrupt and status register 1 (DSI_ISR1) is asserted and an internal soft reset is generated to the DSI Host.

If the timeout low-power reception interrupt enable (TOLPRXIE) bit of the DSI Host interrupt enable register 1 (DSI_IER1) is set, an interrupt is generated. Once the software gets notified by the interrupt, it must reset the D-PHY by de-asserting and asserting the Digital enable (DEN) bit of the DSI Host PHY control register (DSI_PCTLR).

30.8.2 Peripheral response timeout counters

A peripheral may not immediately respond correctly to some received packets. For example, a peripheral receives a read request, but due to its architecture cannot access the RAM for a while (e.g. the panel is being refreshed and takes some time to respond). In this case, set a timeout to ensure that the host waits long enough so that the device is able to process the previous data before receiving the new data or responding correctly to new requests.

Table 204 lists the events belonging to various categories having an associated timeout for peripheral response.

Table 204. List of events of different categories of the PRESP_TO counter

The DSI Host ensures that, on sending an event that triggers a timeout, the D-PHY switches to the Stop state and a counter starts running until it reaches the value of that timeout. The link remains in the LP-11 state and unused until the timeout ends, even if there are other events ready to be transmitted.

Figures 214 to 216 illustrate the flow of counting in the PRESP_TO counter for the three categories listed in Table 204 .

Figure 214. Timing of PRESP_TO after a bus-turn-around

Figure 215. Timing of PRESP_TO after a read request (HS or LP)

Figure 216. Timing of PRESP_TO after a write request (HS or LP)

Table 205 describes the fields used for the configuration of the PRESP_TO counter.

Table 205. PRESP_TO counter configuration

The values in these registers are measured in number of cycles of the lane byte clock. These registers are only used in command mode because in video mode, there is a rigid timing schedule to be met to keep the display properly refreshed and it must not be broken by these or any other timeouts. Setting a given timeout to 0 disables going into LP-11 state and timeout for events of that category.

The read and the write requests in high-speed mode are distinct from the read and the write requests in low-power mode. For example, if HSRD_TOCNT is set to zero and LPRD_TOCNT is set to a non-zero value, a generic read with no parameters does not activate the PRESP_TO counter in high-speed, but it activates the PRESP_TO in low-power.

The DSI Host timeout counter configuration register 4 (DSI_TCCR3) includes a special Presp mode (PM) bit to change the normal behavior of PRESP_TO in Adaptive command

mode for high-speed write operation timeout. When set to 1, this bit allows the RESP_TO from HSWR_TOCNT to be used only once, when both of the following conditions are met:

• • the LTDC VSYNC signal rises and falls
• • the packets originated from the LTDC interface in adapted command mode are transmitted and its FIFO is empty again.

In this scenario, non-adapted command mode requests are not sent to the D-PHY, even if there is traffic from the generic interface ready to be sent, returning them to the Stop state. When it happens, the RESP_TO counter is activated and only when it is completed, the DSI Host sends any other traffic that is ready, as illustrated in Figure 217.

Figure 217. Effect of prep mode at 1

30.9 Functional description: transmission of commands

30.9.1 Transmission of commands in video mode

The DSI Host supports the transmission of commands, both in high-speed and low-power, while in video mode. The DSI Host uses blanking or low-power (BLLP) periods to transmit commands inserted through the APB generic interface. Those periods correspond to the gray areas of Figure 218 .

Figure 218. Command transmission periods within the image area

Commands are transmitted in the blanking periods after the following packets/states:

• • Vertical Sync Start (VSS) packets, if the video sync pulses are not enabled
• • Horizontal sync end (HSE) packets, in the VSA, VBP, and VFP regions
• • Horizontal sync Start (HSS) packets, if the video sync pulses are not enabled in the VSA, VBP, and VFP regions
• • Horizontal active (HACT) state

Besides the areas corresponding to BLLP, large commands can also be sent during the last line of a frame. In that case, the line time for the video mode is violated and the edpihalt signal is set to request the DPI video timing signals to remain inactive. Only if a command does not fit into any BLLP area, it is postponed to the last line, causing the violation of the line time for the video mode, as illustrated in Figure 219 .

Figure 219. Transmission of commands on the last line of a frame

Only one command is transmitted per line, even in the case of the last line of a frame but one command is possible for each line.

There can be only one command sent in low-power per line. However, one low-power command is possible for each line. In high-speed, the DSI Host can send more than one command, as many as it determines to fit in the available time.

The DSI Host avoids sending commands in the last line because it is possible that the last line is shorter than the other ones. For instance, the line time ( \( t_L \) ) could be half a cycle longer than the \( t_L \) on the LTDC interface, that is, each line in the frame taking half a cycle from time for the last line. This results in the last line being \( (\frac{1}{2} \text{ cycle}) \times (\text{number of lines} - 1) \) shorter than \( t_L \) .

The COLM and SHTDN bits of the DSI Wrapper control register (DSI_WCR) are also able to trigger the sending of command packets. The commands are:

• • Color mode ON
• • Color mode OFF
• • Shut down peripheral
• • Turn on peripheral

These commands are not sent in the VACT region. If the low-power command enable (LPCE) bit of the DSI Host video mode configuration register (DSI_VMCR) is set, these commands are sent in low-power mode.

In low-power mode, the largest packet size (LPSIZE) field of the DSI Host low-power mode configuration register (DSI_LPMCR) is used to determine if these commands can be transmitted. It is assumed that largest packet size (LPSIZE) is greater than or equal to four bytes (number of bytes in a short packet), because the DSI Host does not transmit these commands on the last line.

If the frame bus-turn-around acknowledge enable (FBTAEE) bit is set in the DSI Host low-power mode configuration register (DSI_LPMCR), a BTA is generated by DSI Host after the last line of a frame. This may coincide with a write command or a read command. In either case, the LTDC interface is halted until an acknowledge is received (control of the DSI bus is returned to the host).

30.9.2 Transmission of commands in low-power mode

DSI Host can be configured to send the low-power commands during the high-speed video mode transmission.

To enable this feature, set the Low Power command enable (LPCE) bit of the DSI Host video mode configuration register (DSI_VMCR) to 1. In this case, it is necessary to calculate the time available, in bytes, to transmit a command in low-power mode to horizontal front-porch (HFP), vertical sync active (VSA), vertical back-porch (VBP), and vertical front-porch (VFP) regions.

Bits 8 to 13 of the video mode configuration register (DSI_VMCR) register indicate if DSI Host can go to LP when in idle. If the low-power command enable (LPCE) bit is set and non-video packets are in queue, DSI Host ignores the low-power configuration and transmits low-power commands, even if it is not allowed to enter low-power mode in a specific region. After the low-power commands transmission, DSI Host remains in low-power until a sync event occurs.

For example, consider that the VFP is selected as high-speed region (LPVFPE = 1'b0) with LPCE set as a command to transmit in low-power in the VPF region. This command is transmitted in low-power, and the line stays in low-power mode until a new HSS arrives.

Calculating the time to transmit commands in LP mode in the VSA, VBP, and VFP Regions

The largest packet size (LPSIZE) field of the DSI Host low-power mode configuration register (DSI_LPMCR) indicates the time available (in bytes) to transmit a command in low-power mode (based on the escape clock) on a line during the VSA, VBP, and the VFP regions.

Calculation of largest packet size (LPSIZE) depends on the used video mode.

Figure 220 illustrates the timing intervals for the video mode in non-burst with sync pulses, while Figure 221 refers to video mode in burst and non-burst with sync events.

Figure 220. LPSIZE for non-burst with sync pulses

Figure 221. LPSIZE for burst or non-burst with sync events

This time is calculated as follows:

• • \( t_L \) = line time
• • \( t_{H1} \) = time of the HSA pulse for sync pulses mode ( Figure 220 ) or time to send the HSS packet, including EoTp ( Figure 221 )
• • \( t_{\text{HS}\rightarrow\text{LP}} \) = time to enter the low-power mode
• • \( t_{\text{LP}\rightarrow\text{HS}} \) = time to leave the low-power mode
• • \( t_{\text{LPDT}} \) = D-PHY timing related with escape mode entry, LPDT command, and escape exit. According to the D-PHY specification, this value is always 11 bits in LP (or 22 TX escape clock cycles)
• • \( t_{\text{ESCCCLK}} \) = escape clock period as programmed in the TXECKDIV field of the DSI_CCR register
• • \( t_{\text{ESCCCLK}} \) = delay imposed by the DSI Host implementation.

In the above equation, division by eight is done to convert the available time to bytes. Division by two is done because one bit is transmitted every two escape clock cycles. The largest packet size (LPSIZE) field can be compared directly with the size of the command to be transmitted to determine if there is enough time to transmit the command. The maximum size of a command that can be transmitted in low-power mode is limited to 255 bytes by this field. You must program this register to a value greater than or equal to 4 bytes for the transmission of the DCTRL commands, such as shutdown and color in low-power mode.

Consider an example of a frame with 12.4 µs per line and assume an escape clock frequency of 20 MHz and a lane bit rate of 800 Mbits. In this case, it is possible to send 124 bits in escape mode (that is, 124 bit = 12.4 µs * 20 MHz / 2). Still, you need to take into consideration the D-PHY protocol and PHY timings.

The following assumptions are made:

• • lane byte clock period is 10 ns (800 Mbits per lane)
• • escape clock period is 50 ns (DSI_CCR.TXECKDIV = 5)
• • video is transmitted in non-burst mode with sync pulses bounded by HSS and HSE packets
• • DSI is configured for two lanes
• • D-PHY takes 180 ns to transit from low-power to high-speed mode (DSI_DLTCCR.LS2HS_TIME = 18)
• • D-PHY takes 200 ns to transit from high-speed to low-power mode (DSI_DLTCCR.HS2LP_TIME = 20)
• • \( t_{\text{HSA}} = 420 \text{ ns} \) .

In this example, a 13-byte command can be transmitted as follows:

Calculating the time to transmit commands in low-power mode in HFP region

The VACT largest packet size (VLPSIZE) field of the DSI Host low-power mode configuration register (DSI_LPMCR) indicates the time available (in bytes) to transmit a command in low-power mode (based on the escape clock) in the vertical active (VACT) region.

To calculate the value of VACT largest packet size (VLPSIZE), consider the video mode being used. Figure 222 shows the timing intervals for video mode in non-burst with sync pulses, Figure 223 those for video mode in non-burst with sync events, and Figure 224 refers to the burst video mode.

Figure 222. VLPSIZE for non-burst with sync pulses

Figure 223. VLPSIZE for non-burst with sync events

Figure 224. VLPSIZE for burst mode

This time is calculated as follows:

where

• • \( t_L \) = line time
• • \( t_{HSA} \) = time of the HSA pulse (DSI_VHSACR.HSA)
• • \( t_{HBP} \) = time of horizontal back-porch (DSI_VHBPCR.HBP)
• • \( t_{HACT} \) = time of video active. For burst mode, the video active is time compressed and is calculated as \( t_{HACT} = VPSIZE \times Bytes\_per\_Pixel / Number\_Lanes \times t_{Lane\_byte\_clk} \)
• • \( t_{ESCCLK} \) = escape clock period as programmed in TXECKDIV field of the DSI_CCR register.

The VLPSIZE field can be compared directly with the size of the command to be transmitted to determine if there is time to transmit the command.

Consider an example of a frame with 16.4 \( \mu\text{s} \) per line and assume an escape clock frequency of 20 MHz and a lane bit rate of 800 Mbits/s. In this case, it is possible to send 420 bits in escape mode (that is, \( 164 \text{ bits} = 16.4 \mu\text{s} \times 20 \text{ MHz} / 2 \) ). Still, since it is the vertical active region of the frame, take into consideration the HSA, HBP, and HACT timings apart from the D-PHY protocol and PHY timings. The following assumptions are made:

• • number of active lanes is four
• • Lane byte clock period (lanebyteclkperiod) is 10 ns (800 Mbits per lane)
• • escape clock period is 50 ns (DSI_CCR.TXECKDIV = 5)
• • D-PHY takes 180 ns to pass from low-power to high-speed mode (DSI_DLTCCR.LP2HS_TIME = 18)
• • D-PHY takes 200 ns to pass from high-speed to low-power mode (DSI_DLTCCR.HS2LP_TIME = 20)
• • \( t_{\text{HSA}} = 420 \text{ ns} \)
• • \( t_{\text{HBP}} = 800 \text{ ns} \)
• • \( t_{\text{HACT}} = 12800 \text{ ns} \) to send 1280 pixel at 24 bpp
• • video is transmitted in non-burst mode
• • DSI is configured for four lanes.

In this example, consider that video is sent in non-burst mode. The VLPSIZE is calculated as follows:

Only one byte can be transmitted in this period. A short packet (for example, generic short write) requires a minimum of four bytes. Therefore, in this example, commands are not sent in the VACT region.

If burst mode is enabled, more time is available to transmit the commands in the VACT region, because HACT is time compressed.

For burst mode, the VLPSIZE is 5 bytes and then a 4-byte short packet can be sent.

Transmission of commands in different periods

The LPSIZE and VLPSIZE fields allow a simple comparison to determine if a command can be transmitted in any of the BLLP periods.

Figure 225 illustrates the meaning of VLPSIZE and LPSIZE, matching them with the shaded areas and the VACT region.

Figure 225. Location of LPSIZE and VLPSIZE in the image area

30.9.3 Transmission of commands in high-speed

If the LPCE bit of the DSI_VMCR register is 0, the commands are sent in high-speed video mode. In this case, the DSI Host automatically determines the area where each command can be sent and no programming or calculation is required.

30.9.4 Read command transmission

The MRD_TIME field of the register configures the maximum amount of time required to perform a read command in lane byte clock cycles, it is calculated as:

MRD_TIME = time to transmit the read command in low-power mode + time to enter and leave low-power mode + time to return the read data packet from the peripheral device.

The time to return the read data packet from the peripheral depends on the number of bytes read and the escape clock frequency of the peripheral, not the escape clock of the host. The MRD_TIME field is used in both high-speed and low-power mode to determine if there is time to complete a read command in a BLLP period.

In high-speed mode (LPCE = 0), MRD_TIME is calculated as follows:

In low-power mode (LPCE = 1), MRD_TIME is calculated as follows:

• • \( t_{\text{HS}\rightarrow\text{LP}} \) = time to enter the low-power mode
• • \( t_{\text{LP}\rightarrow\text{HS}} \) = time to leave the low-power mode
• • \( t_{\text{LPDT}} \) = D-PHY timing related to escape mode entry, LPDT command, and escape mode exit (according to the D-PHY specification, this value is always 11 bits in LP, or 22 TX escape clock cycles)
• • \( t_{\text{lprd}} \) = read command time in low-power mode ( \( 64 \times \text{TX esc clock} \) )
• • \( t_{\text{read}} \) = time to return the read data packet from the peripheral
• • \( t_{\text{BTA}} \) = time to perform a bus-turn-around (D-PHY dependent).

It is recommended to keep the maximum number of bytes read from the peripheral to a minimum to have sufficient time available to issue the read commands in a line time. Ensure that \( MRD\_TIME \times \text{lane byte clock period} \) is less than \( LPSIZE \times 16 \times \text{escape clock period} \) of the host, otherwise, the read commands are dispatched on the last line of a frame. If it is necessary to read a large number of parameters ( \( > 16 \) ), increase the \( MRD\_TIME \) while the read command is being executed. When the read has completed, decrease the \( MRD\_TIME \) to a lower value.

If a read command is issued on the last line of a frame, the LTDC interface is halted and stays halted until the read command is in progress. The video transmission must be stopped during this period.

30.9.5 Clock lane in low-power mode

To reduce the power consumption of the D-PHY, the DSI Host, when not transmitting in the high-speed mode, allows the clock lane to enter into the low-power mode. The controller automatically handles the transition of the clock lane from HS (clock lane active sending clock) to LP state without direct intervention by the software. This feature can be enabled by configuring the DPCC and the ACR bits of the DSI_CLCR register.

In the command mode, the DSI Host can place the clock lane in the low-power mode when it does not have any HS packets to transmit.

In the video mode (LTDC interface), the DSI Host controller uses its internal video and PHY timing configurations to determine if there is time available for the clock line to enter the low-power mode and not compromise the video data transmission of pixel data and sync events.

Along with a correct configuration of the video mode (see Section 30.5: Functional description: video mode on LTDC interface ), the DSI Host needs to know the time required by the clock lane to go from high-speed to low-power mode and vice-versa. The values required can be obtained from the D-PHY specification: program the DSI_CLTCR register with the following values:

• • \( HS2LP\_TIME \) = time from HS to LP in clock lane / byte clock period in HS ( \( lanebyteclk \) )
• • \( LP2HS\_TIME \) = time from LP to HS in clock lane / byte clock period in HS ( \( lanebyteclk \) )

Based on the programmed values, the DSI Host calculates if there is enough time for the clock lane to enter the low-power mode during inactive regions of the video frame.

The DSI Host decides the best approach to follow regarding power saving out of the three possible scenarios:

• • there is no enough time to go to the low-power mode. Therefore, blanking period is added as shown in Figure 226
• • there is enough time for the data lanes to go to the low-power mode but not enough time for the clock lane to enter the low-power mode, see Figure 227 .
• • there is enough time for both data lanes and clock lane to go to the low-power mode, as in Figure 228 .

Figure 226. Clock lane and data lane in HS

Figure 227. Clock lane in HS and data lanes in LP

Figure 228. Clock lane and data lane in LP

30.10 Functional description: virtual channels

The DSI Host supports choosing the virtual channel (VC) for use for each interface. Using multiple virtual channels, the system can address multiple displays at the same time, when each display has a different virtual channel identifier.

When the LTDC interface is configured for a particular virtual channel, it is possible to use the APB slave generic interface to issue the commands while the video stream is being transmitted. With this, it is possible to send the commands through the ongoing video stream, addressing different virtual channels and thus enable the interface with multiple displays. During the video mode, the video stream transmission has the maximum priority. Therefore, the transmission of sideband packets such as the ones from the generic interface are only transported when there is time available within the video stream transmission. The DSI Host identifies the available time periods and uses them to transport the generic interface packets. Figure 229 illustrates where the DSI Host inserts the packets from the APB generic interface within the video stream transmitted by the LTDC interface.

Figure 229. Command transmission by the generic interface

It is also possible to address the multiple displays with only the generic interface using different virtual channels. Because the generic interface is not restricted to any particular virtual channel through configuration, it is possible to issue the packets with different virtual channels. This enables the interface to time multiplex the packets to be provided to the displays with different virtual channels.

You can use the following configuration registers to select the virtual channel ID associated with transmissions over the LTDC and APB slave generic interfaces:

• • DSI_LVCIIDR.VCID field configures the virtual channel ID that is indexed to the video mode packets using the LTDC interface.
• • DSI_GHCR register configures the packet header (which includes the virtual channel ID to be used) for transmissions using APB slave generic interface.
• • DSI_GVCIDR register configures the virtual channel ID of the read responses to store and return to the generic interface.

30.11 Functional description: video mode pattern generator

The video mode pattern generator allows the transmission of horizontal/vertical color bar and D-PHY BER testing pattern without any stimuli.

The frame requirements must be defined in video registers that are listed in Table 206 .

Table 206. Frame requirement configuration registers

30.11.1 Color bar pattern

The color bar pattern comprises eight bars for white, yellow, cyan, green, magenta, red, blue, and black colors.

Each color width is calculated by dividing the line pixel size (vertical pattern) or the number of lines (horizontal pattern) by eight. In the vertical color bar mode ( Figure 230 ), each single color bar has a width of the number of pixels in a line divided by eight. In case the number of pixels in a line is not divisible by eight, the last color (black) contains the remaining.

In the horizontal color bar mode ( Figure 231 ), each color line has a color width of the number of lines in a frame divided by eight. In case the number of lines in a frame is not divisible by eight, the last color (black) contains the remaining lines.

Figure 230. Vertical color bar mode

Figure 231. Horizontal color bar mode

30.11.2 Color coding

Table 207 shows the RGB components used.

Table 207. RGB components

30.11.3 BER testing pattern

The BER testing pattern simplifies conformance testing. This pattern tests the RX D-PHY capability to receive the data correctly. The following data patterns are required:

• • X bytes of 0xAA (high-frequency pattern, inverted)
• • X bytes of 0x33 (mid-frequency pattern)
• • X bytes of 0xF0 (low-frequency pattern, inverted)
• • X bytes of 0x7F (lone 0 pattern)
• • X bytes of 0x55 (high-frequency pattern)
• • X bytes of 0xCC (mid-frequency pattern, inverted)
• • X bytes of 0x0F (low-frequency pattern)
• • Y bytes of 0x80 (lone 1 pattern).

In most cases, Y is equal to X. However, depending on line length and the color coding used, Y may be different from X. With RGB888 color coding and horizontal resolution in multiples of eight, the pattern shown in Figure 232 appears on the DSI display.

Figure 232. RGB888 BER testing pattern

30.11.4 Video mode pattern generator resolution

Depending on the orientation, BER mode, and color coding, the smallest resolutions accepted by the video mode pattern generator are:

• • BER mode: 8x8
• • horizontal color bar mode: 8x8
• • vertical color bar mode: 8x8.

Vertical pattern

The width of each color bar is determined by the division of horizontal resolution (pixels) for eight test pattern colors. If the horizontal resolution is not divisible by eight, the last color (black) is extended to fill the resolution.

In the example in Figure 233 , the horizontal resolution is 103.

Figure 233. Vertical pattern (103x15)

Horizontal pattern

The width of each color bar is determined by the division of the number of vertical resolution (lines) for eight test pattern colors. If the vertical resolution is not divisible by eight, the last color (black) is extended to fill the resolution, as shown in Figure 234 .

Figure 234. Horizontal pattern (103x15)

30.12 Functional description: D-PHY management

The embedded MIPI® D-PHY is control directly by the DSI Host and is configured through the DSI Wrapper.

A dedicated PLL and a dedicated 1.2 V regulator are also embedded to supply the clock and the power supply to the DSI and D-PHY.

30.12.1 D-PHY configuration

The D-PHY configuration is carried out through the DSI Wrapper thanks to the DSI_WPCR _x registers.

Timing definition

The MIPI® D-PHY manages all the communication timing with dedicated timers. As all the timings are specified in nanoseconds, it is mandatory to configure the unit interval field to ensure the good duration of the timings.

Unit interval is configured through the DSI_WPCR0.UIX4 field. This value defines the bit period in high-speed mode in units of 0.25 ns. If this period is not a multiple of 0.25 ns, the value driven must be rounded down.

As an example, for a 300 Mbit/s link, the unit interval is 3.33 ns, so UIX4 is 13.33. In this case a value of 13 (0x0D) must be written.

Slew-rate and delay tuning on pins

To fine tune DSI communication, slew-rates and delay can be adjusted:

• • slew-rate in high-speed transmission on data lane and clock lane
• • slew-rate in low-power transmission on data lane and clock lane
• • transmission delay in high-speed transmission on data lane and clock lane

Table 208. Slew-rate and delay tuning

The default value for all these parameters is 2'h00. All these values can be programmed only when the DSI is stopped (DSI_WCR.DSIEN = 0 and CR.EN = 0).

Low-power reception filter tuning

The cut-off frequency of the low-pass on low-power receiver can be fine tuned through the LPRXFT field of the DSI_WPCR1 register. The default values is 2'h00 and it can be programmed only when the DSI is stopped (CR.DSIEN = 0 and CR.EN = 0).

Special Sdd control

An additional current path can be activated on both clock lane and data lane to meet the Sdd _TX parameter defined in the MIPI ^® D-PHY Specification.

This activation is done setting the SDDC bit of the DSI_WPCR1 register.

Custom lane configuration

To ease DSI integration, lane pins can be swapped and/or high-speed signals can be inverted on a lane as described in Table 209 .

Table 209. Custom lane configuration

Custom timing configuration

Some of the MIPI ^® D-PHY timing can be tuned for specific purpose as described in Table 210 .

Table 210. Custom timing parameters

All these values can be programmed only when the DSI is stopped (CR.DSIEN = 0 and CR.EN = 0).

30.12.2 Special D-PHY operations

The DSI Wrapper features some control bits to force the D-PHY in some particular state and/or behavior.

Forcing lane state

It is possible to force the data lane and/or the clock lane in TX Stop mode through the bits FTXSMDSL and FTXSMCL of the DSI_WPCR0 register.

Setting this bits causes the respective lane module to immediately jump in transmit control mode and to begin transmitting a stop state (LP-11).

This feature can be used to go back in TX mode after a wrong BTA sequence.

Forcing low-power receiver in low-power mode

The FLPRXLPM bit of the DSI_WPCR1 register enables the low-power mode of the low power receiver (LPRX). When set, the LPRX operates in low-power mode all the time. When not set, the LPRX operates in low-power mode during ULPS only.

Disabling turn of data lane

When set, the TDDL bit of the DSI_WPCR0 register forces the data lane to remain in reception mode even if a bus-turn-around request (BTA) is received from the other side.

30.12.3 Special low-power D-PHY functions

The embedded D-PHY offers specific features to optimize consumption.

Pull-down on lanes

The D-PHY embeds a pull-down on each lane to prevent floating states when the lanes are unused.

When set, the PDEN bit of the DSI_WPCR0 register enables the pull-down on the lanes.

Disabling contention detection on data lanes

The contention detector on the data lane can be turned off to lower the overall D-PHY consumption.

When set, the CDOFFDL bit of the DSI_WPCR0 register disables the contention detection on data lanes.

This can be used in forward escape mode to reduce the static power consumption.

30.12.4 DSI PLL control

The dedicated DSI PLL is controlled through the DSI Wrapper, as shown in Figure 235 (analog blocks and signals in gray, digital signals in black, digital blocks in light blue).

Figure 235. PLL block diagram

The PLL output frequency is configured through the DSI_WRPCR register fields. The VCO frequency and the PLL output frequency are calculated as follows:

where:

• • \( CLK_{IN} \) is in the 4 to 100 MHz range
• • DSI_WRPCR.NDIV is in the 10 to 125 range
• • DSI_WRPCR.IDF is in the 1 to 7 range
• • INFIN is in the 8 to 50 MHz range
• • \( F_{VCO} \) is in the 500 MHz to 1 GHz range
• • DSI_WRPCR.ODF can be 1, 2, 4 or 8
• • PHI is in the 31.25 to 500 MHz range

The PLL is enabled by setting the PLLEN bit in the DSI_WRPCR register.

Once the PLL is locked, the PLLLIF bit is set in the DSI_WISR. If the PLLIE bit is set in the DSI_WIER, an interrupt is generated.

The PLL status (lock or unlock) can be monitored with the PLLLS flag in the DSI_WISR register.

If the PLL gets unlocked, the PLLUIF bit of the DSI_WISR is set. If the PLLUIE bit of the DSI_WIER register is set, an interrupt is generated.

The DSI PLL settings can be changed only when the PLL is disabled.

30.12.5 Regulator control

The DSI regulator providing the 1.2 V is controlled through the DSI Wrapper.

The regulator is enabled setting the REGEN bit of the DSI_WRPCR register.

Once the regulator is ready, the RRIF bit of the DSI_WISR register is set. If the RRIE bit of the DSI_WIER register is set, an interrupt is generated.

The regulator status (ready or not) can be monitored with the RRS flag in the DSI_WISR register.

Note that the D-PHY has no separated Power ON control bit. The power ON/OFF of the D-PHY is done directly enabling the 1.2 V regulator.

When the 1.2 V regulator is disabled, the 3.3 V part of the D-PHY is automatically powered OFF.

30.13 Functional description: interrupts and errors

The interrupts can be generated either by the DSI Host or by the DSI Wrapper.

All the interrupts are merged in one interrupt lane going to the interrupt controller.

30.13.1 DSI Wrapper interrupts

An interrupt can be produced on the following events:

• • tearing effect event
• • end of refresh
• • PLL locked
• • PLL unlocked
• • regulator ready

Separate interrupt enable bits are available for flexibility.

Table 211. DSI Wrapper interrupt requests

30.13.2 DSI Host interrupts and errors

The DSI_ISR0 and DSI_ISR1 registers are associated with error condition reporting. These registers can trigger an interrupt to inform the system about the occurrence of errors.

The DSI Host has one interrupt line that is set high when an error occurs in either the DSI_ISR0 or the DSI_ISR1 register.

The triggering of the interrupt can be masked by programming the mask registers DSI_IER0 and DSI_IER1. By default all errors are masked. When any bit of these registers is set to 1, it enables the interrupt for a specific error. The error bit is always set in the respective DSI_ISR register. The DSI_ISR0 and DSI_ISR1 registers are always cleared after a read operation. The interrupt line is cleared if all registers that caused the interrupt are read.

The interrupt force registers (DSI_FIR0 and DSI_FIR1) are used for test purposes: they allow triggering the interrupt events individually without the need to activate the conditions that trigger the interrupt sources (it is extremely complex to generate the stimuli for that purpose). This feature also facilitates the development and testing of the software associated with the interrupt events. Setting any bit of these registers to 1 triggers the corresponding interrupt.

The light yellow boxes in Figure 236 illustrate the location of some of the errors.

Figure 236. Error sources

Table 212 explains the reasons that set off these interrupts and also explains how to recover from these interrupts.

Table 212. Error causes and recovery

Table 212. Error causes and recovery (continued)

Table 212. Error causes and recovery (continued)

Table 212. Error causes and recovery (continued)

Table 212. Error causes and recovery (continued)

Table 212. Error causes and recovery (continued)

30.14 Programing procedure

To operate the DSI Host the user must be familiar with the MIPI® DSI specification. Every software programmable register is accessible through the APB interface.

30.14.1 Programing procedure overview

The programming procedure for video mode or adapted command mode must respect the following order:

1. 1. Configure the RCC (refer to the RCC chapter)
   • – Enable clock for DSI and LTDC
   • – Configure LTDC PLL, turn it ON and wait for its lock
2. 2. Optionally configure the GPIO (if tearing effect requires GPIO usage for example)
3. 3. Optionally valid the ISR
4. 4. Configure the LTDC (refer to the LTDC chapter)
   • – Program the panel timings
   • – Enable the relevant layers
5. 5. Turn on the DSI regulator and wait for the regulator to be ready, as described in Section 30.12.5
6. 6. Configure the DSI PLL, turn it ON and wait for its lock as described in Section 30.12.4
7. 7. Configure the D-PHY parameters in the DSI Host and the DSI Wrapper to define D-PHY configuration and timing as detailed in Section 30.14.2
8. 8. Configure the DSI Host timings as detailed in Section 30.14.3
9. 9. Configure the DSI Host flow control and DBI interface as detailed in Section 30.14.4
10. 10. Configure the DSI Host LTDC interface as detailed in Section 30.14.5
11. 11. Configure the DSI Host for video mode as detailed in Section 30.14.6 or adapted command mode as detailed in Section 30.14.7
12. 12. Enable the D-PHY setting the DEN bit of the DSI_PCTLR
13. 13. Enable the D-PHY clock lane setting the CKEN bit of the DSI_PCTLR
14. 14. Enable the DSI Host setting the EN bit of the DSI_CR
15. 15. Enable the DSI Wrapper setting the DSIEN bit of the DSI_WCR
16. 16. Optionally send DCS commands through the APB generic interface to configure the display
17. 17. Enable the LTDC in the LTDC
18. 18. Start the LTDC flow through the DSI Wrapper (CR.LTDCEN = 1)

In video mode, the data streaming starts as soon as the LTDC is enabled.

In adapted command mode, the frame buffer update is launched as soon as the CR.LTDCEN bit is set.

30.14.2 Configuring the D-PHY parameters

The D-PHY requires a specific configuration prior starting any communications. The configuration parameters are stored either in the DSI Host or the DSI Wrapper.

Configuring the D-PHY parameters in the DSI Wrapper

The DSI Wrapper can be used to fine tune either timing or physical parameters of the D-PHY. This operation is not required for a standard usage of the D-PHY. All the fields and parameters are detailed in the register description of the DSI Wrapper.

Only one field is mandatory to properly start the D-PHY: the unit interval multiplied by 4 (UIX4) field of the DSI Wrapper PHY configuration register 1 (DSI_WPCR0).

This field defines the bit period in high-speed mode in unit of 0.25 ns, and is used as a timebase for all the timings managed by the D-PHY.

If the link is working at 600 Mbit/s, the unit interval shall be 1.667 ns, that becomes 6.667 ns when multiplied by four. When rounded down, a value of 6 must be written in the UIX4 field of the DSI_WPCR0 register.

Configuring the D-PHY parameters in the DSI Host

The DSI Host stores the configuration of D-PHY timing parameters and number of lanes.

The following fields must be configured prior to any startup:

• • Number of data lanes in the DSI_PCONF register
• • Automatic clock lane control (ACR) in the DSI_CLCR register
• • Clock control (DPCC) in the DSI_CLCR register
• • Time for LP/HS and HS/LP transitions for both clock lane and data lanes in DSI_CLTCR and DSI_DLTCR registers
• • Stop wait time in the DSI_PCONF register

30.14.3 Configuring the DSI Host timing

All the protocol timing must be configured in the DSI Host.

Clock divider configuration

Two clocks are generated internally

• • Timeout clock
• • TX escape clock.

The timeout clock is used as the timing unit in the configuration of HS to LP and LP to HS transition error. Its division factor is configured by the timeout clock division (TOCKDIV) field of the DSI Host clock control register (DSI_CCR).

The TX escape clock is used in low-power transmission. Its division factor is configured by the TX escape clock division (TXECKDIV) field of the DSI Host clock control register (DSI_CCR) relatively to the lanebyteclock. Its typical value must be around 20 MHz.

Timeout configuration

The timings for timeout management as described in Section 30.8 are configured in the DSI Host timeout counter configuration registers (DSI_TCCR0 to DSI_TCCR5).

30.14.4 Configuring flow control and DBI interface

The flow control is configured thanks to the DSI Host protocol configuration register (DSI_PCR). The configuration parameters are the following

• • CRC reception enable (CRCRXE bit)
• • ECC reception enable (ECCRXE bit)
• • BTA enable (BTAE bit)
• • EoTp reception enable (ETRXE bit)
• • EoTp transmission enable (ETTXE bit)

Their values depends on the protocol to be used for the communication with the DSI display.

The virtual channel ID used for the generic DBI interface must be configured by the virtual channel ID (VCID) field of the DSI Host generic VCID register (DSI_GVCIDR).

All the DCS command, depending on their type, can be transmitted or received either in high-speed or low-power. For each of them, a dedicated configuration bit must be programmed in the DSI Host command mode configuration register (DSI_CMCR).

Acknowledge request for packet or tearing effect event must also be configured in the DSI Host command mode configuration register (DSI_CMCR).

30.14.5 Configuring the DSI Host LTDC interface

As the DSI Host is interface to the system through the LTDC for video mode or adapted command mode, the DSI Wrapper perform a low level interfacing in between.

The parameter programmed into the DSI Wrapper must be aligned with the parameters programmed into the LTDC and the DSI Host.

The following fields must be configured:

• • Virtual channel ID in the virtual channel ID (VCID) field of the DSI Host LTDC VCID register (DSI_LVCIDR).
• • Color coding (COLC) field of the DSI Host LTDC color coding register (DSI_LCOLCR) and the color multiplexing (COLMUX) in the DSI Wrapper configuration register (DSI_WCFGGR).
• • If loose packets are used for 18-bit mode, the loosely packet enable (LPE) bit of the DSI Host LTDC color coding register (DSI_LCOLCR) must be set.
• • The HSYNC polarity in the HSync polarity (HSP) bit of the DSI Host LTDC polarity configuration register (DSI_LPCR).
• • The VSYNC polarity in the VSync polarity (VSP) bit of the DSI Host LTDC polarity configuration register (DSI_LPCR) and in the VSync polarity (VSPOL) bit of the DSI Wrapper configuration register (DSI_WCFGGR).
• • The DATA ENABLE polarity data enable polarity (DEP) bit of the DSI Host LTDC polarity configuration register (DSI_LPCR).

30.14.6 Configuring the video mode

The video mode configuration defines the behavior of the controller in low-power for command transmission, the type of video transmission (burst or non-burst mode) and the panel horizontal and vertical timing:

• • Select the video transmission mode to define how the processor requires the video line to be transported through the DSI link.
  • – Configure the low-power transitions in the DSI_VMCR to define the video periods which are permitted to go to low-power if there is time available to do so.
  • – Configure if the controller must request the peripheral acknowledge message at the end of frames (DSI_VMCR.FBTAEE).
  • – Configure if commands are to be transmitted in low-power (DSI_VMCR.LPE).
• • Select the video mode type
  • – Burst mode:
    Configure the video mode type (DSI_VMCR.VMT) with value 2'b1x.
    Configure the video packet size (DSI_VPCR.VPSIZE) with the size of the active line period, measured in pixels.
    The registers DSI_VCCR and DSI_VNPCR are ignored by the DSI Host.
  • – Non-burst mode:
    Configure the video mode type (DSI_VMCR.VMT) with 2'b00 to enable the transmission of sync pulses or with 2'b01 to enable the transmission of sync events.
    Configure the video packet size (DSI_VPCR.VPSIZE) with the number of pixels to be transmitted in a single packet. Selecting this value depends on the available memory of the attached peripheral, if the data is first stored, or on the memory you want to select for the FIFO in DSI Host.
    Configure the number of chunks (DSI_VCCR.NUMC) with the number of packets to be transmitted per video line. The value of \( VPSIZE * NUMC \) is the number of pixels per line of video, except if NUMC is 0, which disables the multi-packets. If you set it to 1, there is still only one packet per line, but it can be part of a chunk, followed by a null packet.
    Configure the null packet size (DSI_VNPCR.NPSIZE) with the size of null packets to be inserted as part of the chunks. Setting it to 0 disables null packets.
• • Define the video horizontal timing configuration as follows:
  • – Configure the horizontal line time (DSI_VLCR.HLINE) with the time taken by a LTDC video line measured in cycles of lane byte clock (for a clock lane at 500 MHz the lane byte clock period is 8 ns). When the periods of LTDC clock and lane byte clock are not multiples, the value to program the DSI_VLCR.HLINE needs to be rounded. A timing mismatch is introduced between the lines due to the rounding of configuration values. If the DSI Host is configured not to go to low-power, this timing divergence accumulates on every line, introducing a significant amount of mismatch towards the end of the frame. The reason for this is that the DSI Host cannot re-synchronize on every new line because it transmits the blanking packets when the horizontal sync event occurs on the LTDC interface. However, the accumulated mismatch must become extinct on the last line of a frame, where, according to the DSI specification, the link must always return to low-power regaining synchronization, when a new frame starts on a vertical sync event. If the accumulated timing mismatch is greater than the time in low-power on the last

line, a malfunction occurs. This phenomenon can be avoided by configuring the DSI Host to go to low-power once per line.

• – Configure the horizontal sync duration (DSI_VHSACR.HSA) with the time taken by a LTDC horizontal sync active period measured in cycles of lane byte clock (normally a period of 8 ns).
• – Configure the horizontal back-porch duration (DSI_VHBPCR.HBP) with the time taken by the LTDC horizontal back-porch period measured in cycles of lane byte clock (normally a period of 8 ns). Special attention must be given to the calculation of this parameter.
• • Define the vertical line configuration:
  • – Configure the vertical sync duration (DSI_VVSACR.VSA) with the number of lines existing in the LTDC vertical sync active period.
  • – Configure the vertical back-porch duration (DSI_VVBPCR.VBP) with the number of lines existing in the LTDC vertical back-porch period.
  • – Configure the vertical front-porch duration (DSI_VVFPCTR.VFP) with the number of lines existing in the LTDC vertical front-porch period.
  • – Configure the vertical active duration (DSI_VVACR.VA) with the number of lines existing in the LTDC vertical active period.

Figure 237 illustrates the steps for configuring the DPI packet transmission.

Figure 237. Video packet transmission configuration flow diagram

graph TD; A[Global configuration
Configure the DPI I/F] --> B{Burst Mode}; B -- NO --> C[Determine the DSI link to pixel ratio]; B -- YES --> D[Configure video_packet_size]; C --> E{Enable multiple packets}; E -- YES --> F[Determine number of pixel per packet
Calculate the number of chunks
Determine the chunk overhead
(needs to be ≥ 12 or = 6)]; E -- NO --> G[Determine number of pixel per packet]; E --> H[/If the DSI link to pixel ratio is > 1/]; F --> I{Enable null packets}; I -- YES --> J[Null packet size]; I -- NO --> K[Calculate:
Hline_time - Hsa_time - Hbp_time

Configure:
VSA lines- VBP lines - Vact lines - VFP lines]; I --> L[/If the DSI chunk overhead is ≥ 12/]; G --> K; D --> K;

Example of video configuration

The following is an example of video packet transmission configuration:

Video resolution:

• • PCLK period = 50 ns
• • HSA = 8 PCLK
• • HBP = 8 PCLK
• • HACT = 480 PCLK
• • HFP = 24 PCLK
• • VSA = 2 lines
• • VBP = 2 lines
• • VACT = 640 lines
• • VFP = 4 lines

Configuration steps:

• • Video transmission mode configuration:
  1. a) Configure the low-power transitions:
     \( DSI\_VMCR[13:8] = 6'b111111 \) , to enable LP in all video period.
  2. b) \( DSI\_VMCR.FBTAEE = 1 \) , for the DSI Host to request an acknowledge response message from the peripheral at the end of each frame.
• • To use the burst mode, follow these steps:
  \( DSI\_VMCR.VMT = 2'b1x \)
  \( DSI\_VPCR.VPSIZE = 480 \)
• • Horizontal timing configuration:
  • – \( DSI\_VLCR.HLINE = (HSA + HBP + HACT + HFP) * (PCLK period / Clk lane byte period) = (8 + 8 + 480 + 24) * (50 / 8) = 3250 \)
  • – \( DSI\_VHSACR.HSA = HSA * (PCLK period / Clk lane byte period) = 8 * (50 / 8) = 50 \)
  • – \( DSI\_VHBPCR.HBP = HBP * (PCLK period / Clk lane byte period) = 8 * (50 / 8) = 50 \)
• • Vertical line configuration:
  • – \( DSI\_VVSACR.VSA = 2 \)
  • – \( DSI\_VVBPCR.VBP = 2 \)
  • – \( DSI\_VVFPCR.VFP = 4 \)
  • – \( DSI\_VVACR.VA = 640 \)

30.14.7 Configuring the adapted command mode

The adapted command mode requires the following parameters to be configured:

• • Command size (CMDSIZE) field of the DSI Host LTDC command configuration register (DSI_LCCR) to define the maximum allowed size for a write memory command.
• • The tearing effect source (TESRC) and optionally tearing effect polarity (TEPOL) bits of the DSI Wrapper configuration register (DSI_WCFGR).
• • The automatic refresh (AR) bit of the DSI Wrapper configuration register (DSI_WCFGR) if the display needs to be updated automatically each time a tearing effect event is received.

30.14.8 Configuring the video mode pattern generator

DSI Host can transmit a color bar pattern without horizontal/vertical color bar and D-PHY BER testing pattern without any kind of stimuli.

Figure 238 shows the programming sequence to send a test pattern:

1. 1. Configure the DSI_MCR register to enable video mode. Configure the video mode type using DSI_VMCR.VMT.
2. 2. Configure the DSI_LCOLCR register.
3. 3. Configure the frame using registers shown in Figure 239 (where the gray area indicates the transferred pixels).
4. 4. Configure the pattern generation mode (DSI_VMCR.PGM) and the pattern orientation (DSI_VMCR.PGO), and enable them (DSI_VMCR.PGE).

Figure 238. Programming sequence to send a test pattern

graph TD; Start(( )) --> A[Video Mode selection]; A --> B[Color coding configuration]; B --> C[Video frame configuration]; C --> D[Video pattern generator configuration]; D --> End(( ));

Figure 239. Frame configuration registers

MSv35877V1

Note: The number of pixels of payload is restricted to a multiple of a value provided in Table 202.

30.14.9 Managing ULPM

There are two ways to configure the software to enter and exit the ULPM:

• • enter and exit the ULPM with the D-PHY PLL running (a faster process)
• • enter and exit the ULPM with the D-PHY PLL turned off (a more efficient process in terms of power consumption).

Clock management for ULPM sequence

The ULPM management state machine is working on the lanebyteclock provided by the D-PHY.

Because the D-PHY is providing the lanebyteclock only when the clock lane is not in ULPM state, it is mandatory to switch the lanebyteclock source of the DSI Host before starting the ULPM mode entry sequence.

The lanebyteclock source is controlled by the RCC. It can be

• • the lanebyteclock provided by the D-PHY (for all modes except ULPM)
• • a clock generated by the system PLL (for ULPM)

Process flow to enter the ULPM

Implement the process described in detail in the following procedure to enter the ULPM on both clock lane and data lanes:

1. 1. Verify the initial status of the DSI Host:
   • – DSI_PCTLR[2:1] = 2'h3
   • – DSI_WRPCR.PLLEN = 1'h1 and DSI_WRPCR.REGEN = 1'h1
   • – DSI_PUCR[3:0] = 4'h0
   • – DSI_PTTTCR[3:0] = 4'h0
   • – Verify that all active lanes are in Stop state and the D-PHY PLL is locked:
     One-lane configuration: DSI_PSR[6:4] = 3'h3 and DSI_PSR[1] = 1'h0 and DSI_WISR.PLLS = 1'h1
     Two-lanes configuration: DSI_PSR[8:4] = 5'h1B and DSI_PSR[1] = 1'h0 and DSI_WISR.PLLS = 1'h1
2. 2. Switch the lanebyteclock source in the RCC from D-PHY to system PLL
3. 3. Set DSI_PUCR[3:0] = 4'h5 to enter ULPM in the data and the clock lanes.
4. 4. Wait until the D-PHY active lanes enter into ULPM:
   • – One-lane configuration: DSI_PSR[6:1] = 6'h00
   • – Two-lanes configuration: DSI_PSR[8:1] = 8'h00
   The DSI Host is now in ULPM.
5. 5. Turn off the D-PHY PLL by setting DSI_WRPCR.PLLEN = 1'b0

Process flow to exit the ULPM

Implement the process flow described in the following procedure to exit the ULPM on both clock lane and data lanes:

1. 1. Verify that all active lanes are in ULPM:
   • – One-lane configuration: DSI_PSR[6:1] = 6'h00
   • – Two-lanes configuration: DSI_PSR[8:1] = 8'h00
2. 2. Turn on the D-PHY PLL by setting DSI_WRPCR.PLLLEN = 1'b1.
3. 3. Wait until D-PHY PLL locked
   • – DSI_WISR.PLLS = 1'b1
4. 4. Without de-asserting the ULPM request bits, assert the exit ULPM bits by setting DSI_PUCR[3:0] = 4'hF.
5. 5. Wait until all active lanes exit ULPM:
   • – One-lane configuration:
     DSI_PSR[5] = 1'b1
     DSI_PSR[3] = 1'b1
   • – Two-lanes configuration:
     DSI_PSR[8] = 1'b1
     DSI_PSR[5] = 1'b1
     DSI_PSR[3] = 1'b1
6. 6. Wait for 1 ms.
7. 7. De-assert the ULPM requests and the ULPM exit bits by setting DSI_PUCR [3:0] = 4'h0.
8. 8. Switch the lanbyteclock source in the RCC from system PLL to D-PHY
9. 9. The DSI Host is now in Stop state and the D-PHY PLL is locked:
   • – One-lane configuration:
     DSI_PSR[6:4] = 3'h3
     DSI_PSR[1] = 1'h0
     DSI_WRPCR.PLLLEN = 1'b1
   • – Two-lanes configuration:
     DSI_PSR[8:4] = 5'h1B
     DSI_PSR[1] = 1'h0
     DSI_WRPCR.PLLLEN = 1'b1

30.15 DSI Host registers

30.15.1 DSI Host version register (DSI_VR)

Address offset: 0x0000

Reset value: 0x3133 302A

Bits 31:0 VERSION[31:0] : Version of the DSI Host

This read-only register contains the version of the DSI Host

30.15.2 DSI Host control register (DSI_CR)

Address offset: 0x0004

Reset value: 0x0000 0000

Bits 31:1 Reserved, must be kept at reset value.

Bit 0 EN : Enable

This bit configures the DSI Host in either power-up mode or to reset.

0: DSI Host disabled (under reset)

1: DSI Host enabled

30.15.3 DSI Host clock control register (DSI_CCR)

Address offset: 0x0008

Reset value: 0x0000 0000

Bits 31:16 Reserved, must be kept at reset value.

Bits 15:8 TOCKDIV[7:0] : Timeout clock division

This field indicates the division factor for the timeout clock used as the timing unit in the configuration of HS to LP and LP to HS transition error.

Bits 7:0 TXECKDIV[7:0] : TX escape clock division

This field indicates the division factor for the TX escape clock source (lanebyteclk). The values 0 and 1 stop the TX_ESC clock generation.

30.15.4 DSI Host LTDC VCID register (DSI_LVCIDR)

Address offset: 0x000C

Reset value: 0x0000 0000

Bits 31:2 Reserved, must be kept at reset value.

Bits 1:0 VCID[1:0] : Virtual channel ID

These bits configure the virtual channel ID for the LTDC interface traffic.

30.15.5 DSI Host LTDC color coding register (DSI_LCOLCR)

Address offset: 0x0010

Reset value: 0x0000 0000

Bits 31:9 Reserved, must be kept at reset value.

Bit 8 LPE : Loosely packet enable

This bit enables the loosely packed variant to 18-bit configuration

0: Loosely packet variant disabled

1: Loosely packet variant enabled

Bits 7:4 Reserved, must be kept at reset value.

Bits 3:0 COLC[3:0] : Color coding

This field configures the DPI color coding.
0000: 16-bit configuration 1
0001: 16-bit configuration 2
0010: 16-bit configuration 3
0011: 18-bit configuration 1
0100: 18-bit configuration 2
0101: 24-bit
Others: Reserved

30.15.6 DSI Host LTDC polarity configuration register (DSI_LPCR)

Address offset: 0x0014

Reset value: 0x0000 0000

Bits 31:3 Reserved, must be kept at reset value.

Bit 2 HSP : HSYNC polarity

This bit configures the polarity of HSYNC pin.
0: HSYNC pin active high (default)
1: VSYNC pin active low

Bit 1 VSP : VSYNC polarity

This bit configures the polarity of VSYNC pin.
0: Shutdown pin active high (default)
1: Shutdown pin active low

Bit 0 DEP : Data enable polarity

This bit configures the polarity of data enable pin.
0: Data enable pin active high (default)
1: Data enable pin active low

30.15.7 DSI Host low-power mode configuration register (DSI_LPMCR)

Address offset: 0x0018

Reset value: 0x0000 0000

Bits 31:24 Reserved, must be kept at reset value.

Bits 23:16 LPSIZE[7:0] : Largest packet size

This field is used for the transmission of commands in low-power mode. It defines the size, in bytes, of the largest packet that can fit in a line during VSA, VBP and VFP regions.

Bits 15:8 Reserved, must be kept at reset value.

Bits 7:0 VLPSIZE[7:0] : VACT largest packet size

This field is used for the transmission of commands in low-power mode. It defines the size, in bytes, of the largest packet that can fit in a line during VACT regions.

30.15.8 DSI Host protocol configuration register (DSI_PCR)

Address offset: 0x002C

Reset value: 0x0000 0000

Bits 31:5 Reserved, must be kept at reset value.

Bit 4 CRCRXE : CRC reception enable

This bit enables the CRC reception and error reporting.

0: CRC reception is disabled.

1: CRC reception is enabled.

Bit 3 ECCRXE : ECC reception enable

This bit enables the ECC reception, error correction and reporting.

0: ECC reception is disabled.

1: ECC reception is enabled.

Bit 2 BTAE : Bus-turn-around enable

This bit enables the bus-turn-around (BTA) request.

0: Bus-turn-around request is disabled.

1: Bus-turn-around request is enabled.

Bit 1 ETRXE : EoTp reception enable

This bit enables the EoTp reception.

0: EoTp reception is disabled.

1: EoTp reception is enabled.

Bit 0 ETTXE : EoTp transmission enable

This bit enables the EoTP transmission.

0: EoTp transmission is disabled.

1: EoTp transmission is enabled.

30.15.9 DSI Host generic VCID register (DSI_GVCIDR)

Address offset: 0x0030

Reset value: 0x0000 0000

Bits 31:2 Reserved, must be kept at reset value.

30.15.10 DSI Host mode configuration register (DSI_MCR)

Address offset: 0x0034

Reset value: 0x0000 0001

Bits 31:1 Reserved, must be kept at reset value.

30.15.11 DSI Host video mode configuration register (DSI_VMCR)

Address offset: 0x0038

Reset value: 0x0000 0000

Bits 31:25 Reserved, must be kept at reset value.

Bit 24 PGO : Pattern generator orientation

This bit configures the color bar orientation.

0: Vertical color bars.

1: Horizontal color bars.

Bits 23:21 Reserved, must be kept at reset value.

Bit 20 PGM : Pattern generator mode

This bit configures the pattern generator mode.

0: Color bars (horizontal or vertical).

1: BER pattern (vertical only).

Bits 19:17 Reserved, must be kept at reset value.

Bit 16 PGE : Pattern generator enable

This bit enables the video mode pattern generator.

0: Pattern generator is disabled.

1: Pattern generator is enabled.

Bit 15 LPCE : Low-power command enable

This bit enables the command transmission only in low-power mode.

0: Command transmission in low-power mode is disabled.

1: Command transmission in low-power mode is enabled.

Bit 14 FBTAAE : Frame bus-turn-around acknowledge enable

This bit enables the request for an acknowledge response at the end of a frame.

0: Acknowledge response at the end of a frame is disabled.

1: Acknowledge response at the end of a frame is enabled.

Bit 13 LPHFPE : Low-power horizontal front-porch enable

This bit enables the return to low-power inside the horizontal front-porch (HFP) period when timing allows.

0: Return to low-power inside the HFP period is disabled.

1: Return to low-power inside the HFP period is enabled.

Bit 12 LPHBPE : Low-power horizontal back-porch enable

This bit enables the return to low-power inside the horizontal back-porch (HBP) period when timing allows.

0: Return to low-power inside the HBP period is disabled.

1: Return to low-power inside the HBP period is enabled.

Bit 11 LPVAE : Low-power vertical active enable

This bit enables to return to low-power inside the vertical active (VACT) period when timing allows.

0: Return to low-power inside the VACT is disabled.

1: Return to low-power inside the VACT is enabled.

Bit 10 LPVFPE : Low-power vertical front-porch enable

This bit enables to return to low-power inside the vertical front-porch (VFP) period when timing allows.

0: Return to low-power inside the VFP is disabled.

1: Return to low-power inside the VFP is enabled.

Bit 9 LPVBPE : Low-power vertical back-porch enable

This bit enables to return to low-power inside the vertical back-porch (VBP) period when timing allows.
0: Return to low-power inside the VBP is disabled.
1: Return to low-power inside the VBP is enabled.

Bit 8 LPVSAE : Low-power vertical sync active enable

This bit enables to return to low-power inside the vertical sync time (VSA) period when timing allows.
0: Return to low-power inside the VSA is disabled.
1: Return to low-power inside the VSA is enabled.

Bits 7:2 Reserved, must be kept at reset value.

Bits 1:0 VMT[1:0] : Video mode type

This field configures the video mode transmission type :
00: Non-burst with sync pulses.
01: Non-burst with sync events.
1x: Burst mode

30.15.12 DSI Host video packet configuration register (DSI_VPCR)

Address offset: 0x003C

Reset value: 0x0000 0000

Bits 31:14 Reserved, must be kept at reset value.

Bits 13:0 VPSIZE[13:0] : Video packet size

This field configures the number of pixels in a single video packet.
For 18-bit not loosely packed data types, this number must be a multiple of 4.
For YCbCr data types, it must be a multiple of 2 as described in the DSI specification.

30.15.13 DSI Host video chunks configuration register (DSI_VCCR)

Address offset: 0x0040

Reset value: 0x0000 0000

Bits 31:13 Reserved, must be kept at reset value.

Bits 12:0 NUMC[12:0] : Number of chunks

This register configures the number of chunks to be transmitted during a line period (a chunk consists of a video packet and a null packet).

If set to 0 or 1, the video line is transmitted in a single packet.

If set to 1, the packet is part of a chunk, so a null packet follows it if NPSIZE > 0. Otherwise, multiple chunks are used to transmit each video line.

30.15.14 DSI Host video null packet configuration register (DSI_VNPCR)

Address offset: 0x0044

Reset value: 0x0000 0000

Bits 31:13 Reserved, must be kept at reset value.

Bits 12:0 NPSIZE[12:0] : Null packet size

This field configures the number of bytes inside a null packet.

Setting to 0 disables the null packets.

30.15.15 DSI Host video HSA configuration register (DSI_VHSACR)

Address offset: 0x0048

Reset value: 0x0000 0000

Bits 31:12 Reserved, must be kept at reset value.

Bits 11:0 HSA[11:0] : Horizontal synchronism active duration

This field configures the horizontal synchronism active period in lane byte clock cycles.

30.15.16 DSI Host video HBP configuration register (DSI_VHBPCR)

Address offset: 0x004C

Reset value: 0x0000 0000

Bits 31:12 Reserved, must be kept at reset value.

Bits 11:0 HBP[11:0] : Horizontal back-porch duration

This field configures the horizontal back-porch period in lane byte clock cycles.

30.15.17 DSI Host video line configuration register (DSI_VLCR)

Address offset: 0x0050

Reset value: 0x0000 0000

Bits 31:15 Reserved, must be kept at reset value.

Bits 14:0 HLINE[14:0] : Horizontal line duration

This field configures the total of the horizontal line period (HSA+HBP+HACT+HFP) counted in lane byte clock cycles.

30.15.18 DSI Host video VSA configuration register (DSI_VVSACR)

Address offset: 0x0054

Reset value: 0x0000 0000

Bits 31:10 Reserved, must be kept at reset value.

Bits 9:0 VSA[9:0] : Vertical synchronism active duration

This field configures the vertical synchronism active period measured in number of horizontal lines.

30.15.19 DSI Host video VBP configuration register (DSI_VVBPCR)

Address offset: 0x0058

Reset value: 0x0000 0000

Bits 31:10 Reserved, must be kept at reset value.

Bits 9:0 VBP[9:0] : Vertical back-porch duration

This field configures the vertical back-porch period measured in number of horizontal lines.

30.15.20 DSI Host video VFP configuration register (DSI_VVFPPCR)

Address offset: 0x005C

Reset value: 0x0000 0000

Bits 31:10 Reserved, must be kept at reset value.

Bits 9:0 VFP[9:0] : Vertical front-porch duration

This field configures the vertical front-porch period measured in number of horizontal lines.

30.15.21 DSI Host video VA configuration register (DSI_VVACR)

Address offset: 0x0060

Reset value: 0x0000 0000

Bits 31:14 Reserved, must be kept at reset value.

Bits 13:0 VA[13:0] : Vertical active duration

This field configures the vertical active period measured in number of horizontal lines.

30.15.22 DSI Host LTDC command configuration register (DSI_LCCR)

Address offset: 0x0064

Reset value: 0x0000 0000

Bits 31:16 Reserved, must be kept at reset value.

Bits 15:0 CMDSIZE[15:0] : Command size

This field configures the maximum allowed size for an LTDC write memory command, measured in pixels. Automatic partitioning of data obtained from LTDC is permanently enabled.

30.15.23 DSI Host command mode configuration register (DSI_CMCR)

Address offset: 0x0068

Reset value: 0x0000 0000

Bits 31:25 Reserved, must be kept at reset value.

Bit 24 MRDPS : Maximum read packet size

This bit configures the maximum read packet size command transmission type:

0: High-speed

1: Low-power

Bits 23:20 Reserved, must be kept at reset value.

Bit 19 DLWTX : DCS long write transmission

This bit configures the DCS long write packet command transmission type:

0: High-speed

1: Low-power

Bit 18 DSR0TX : DCS short read zero parameter transmission

This bit configures the DCS short read packet with zero parameter command transmission type:

0: High-speed

1: Low-power

Bit 17 DSW1TX : DCS short read one parameter transmission

This bit configures the DCS short read packet with one parameter command transmission type:

0: High-speed

1: Low-power

Bit 16 DSW0TX : DCS short write zero parameter transmission

This bit configures the DCS short write packet with zero parameter command transmission type:

0: High-speed

1: Low-power

Bit 15 Reserved, must be kept at reset value.

Bit 14 GLWTX : Generic long write transmission

This bit configures the generic long write packet command transmission type :

0: High-speed

1: Low-power

Bit 13 GSR2TX : Generic short read two parameters transmission

This bit configures the generic short read packet with two parameters command transmission type:

0: High-speed

1: Low-power

Bit 12 GSR1TX : Generic short read one parameters transmission

This bit configures the generic short read packet with one parameters command transmission type:

0: High-speed

1: Low-power

Bit 11 GSR0TX : Generic short read zero parameters transmission

This bit configures the generic short read packet with zero parameters command transmission type:

0: High-speed

1: Low-power

Bit 10 GSW2TX : Generic short write two parameters transmission

This bit configures the generic short write packet with two parameters command transmission type:

0: High-speed

1: Low-power

Bit 9 GSW1TX : Generic short write one parameters transmission

This bit configures the generic short write packet with one parameters command transmission type:

0: High-speed

1: Low-power

Bit 8 GSW0TX : Generic short write zero parameters transmission

This bit configures the generic short write packet with zero parameters command transmission type:

0: High-speed

1: Low-power

Bits 7:2 Reserved, must be kept at reset value.

Bit 1 ARE : Acknowledge request enable

This bit enables the acknowledge request after each packet transmission:

0: Acknowledge request is disabled.

1: Acknowledge request is enabled.

Bit 0 TEARE : Tearing effect acknowledge request enable

This bit enables the tearing effect acknowledge request:

0: Tearing effect acknowledge request is disabled.

1: Tearing effect acknowledge request is enabled.

30.15.24 DSI Host generic header configuration register (DSI_GHCR)

Address offset: 0x006C

Reset value: 0x0000 0000

Bits 31:24 Reserved, must be kept at reset value.

Bits 23:16 WCMSB[7:0] : WordCount MSB

This field configures the most significant byte of the header packet's word count for long packets, or data 1 for short packets.

Bits 15:8 WCLSB[7:0] : WordCount LSB

This field configures the less significant byte of the header packet word count for long packets, or data 0 for short packets.

Bits 7:6 VCID[1:0] : Channel

This field configures the virtual channel ID of the header packet.

Bits 5:0 DT[5:0] : Type

This field configures the packet data type of the header packet.

30.15.25 DSI Host generic payload data register (DSI_GPDR)

Address offset: 0x0070

Reset value: 0x0000 0000

Bits 31:24 DATA4[7:0] : Payload byte 4

This field indicates the byte 4 of the packet payload.

Bits 23:16 DATA3[7:0] : Payload byte 3

This field indicates the byte 3 of the packet payload.

Bits 15:8 DATA2[7:0] : Payload byte 2

This field indicates the byte 2 of the packet payload.

Bits 7:0 DATA1[7:0] : Payload byte 1

This field indicates the byte 1 of the packet payload.

30.15.26 DSI Host generic packet status register (DSI_GPSR)

Address offset: 0x0074

Reset value: 0x0000 0015

Bits 31:7 Reserved, must be kept at reset value.

Bit 6 RCB : Read command busy

This bit is set when a read command is issued and cleared when the entire response is stored in the FIFO:

0: No read command on going

1: Read command on going

Bit 5 PRDFF : Payload read FIFO full

This bit indicates the full status of the generic read payload FIFO:

0: Read payload FIFO not full

1: Read payload FIFO full.

Bit 4 PRDFE : Payload read FIFO empty

This bit indicates the empty status of the generic read payload FIFO:

0: Read payload FIFO not empty

1: Read payload FIFO empty

Bit 3 PWRFF : Payload write FIFO full

This bit indicates the full status of the generic write payload FIFO:

0: Write payload FIFO not full

1: Write payload FIFO full

Bit 2 PWRFE : Payload write FIFO empty

This bit indicates the empty status of the generic write payload FIFO:

0: Write payload FIFO not empty

1: Write payload FIFO empty

Bit 1 CMDFF : Command FIFO full

This bit indicates the full status of the generic command FIFO:

0: Write payload FIFO not full

1: Write payload FIFO full

Bit 0 CMDFE : Command FIFO empty

This bit indicates the empty status of the generic command FIFO:

0: Write payload FIFO not empty

1: Write payload FIFO empty

30.15.27 DSI Host timeout counter configuration register 0 (DSI_TCCR0)

Address offset: 0x0078

Reset value: 0x0000 0000

Bits 31:16 HSTX_TOCNT[15:0] : High-speed transmission timeout counter

This field configures the timeout counter that triggers a high-speed transmission timeout contention detection (measured in TOCKDIV cycles).

If using the non-burst mode and there is no enough time to switch from high-speed to low-power and back in the period from one line data finishing to the next line sync start, the DSI link returns the low-power state once per frame, then configure the TOCKDIV and HSTX_TOCNT to be in accordance with:

In burst mode, RGB pixel packets are time-compressed, leaving more time during a scan line. Therefore, if in burst mode and there is enough time to switch from high-speed to low-power and back in the period from one line data finishing to the next line sync start, the DSI link can return low-power mode and back in this time interval to save power. For this, configure the TOCKDIV and HSTX_TOCNT to be in accordance with:

Bits 15:0 LPRX_TOCNT[15:0] : Low-power reception timeout counter

This field configures the timeout counter that triggers a low-power reception timeout contention detection (measured in TOCKDIV cycles).

30.15.28 DSI Host timeout counter configuration register 1 (DSI_TCCR1)

Address offset: 0x007C

Reset value: 0x0000 0000

Bits 31:16 Reserved, must be kept at reset value.

Bits 15:0 HSRD_TOCNT[15:0] : High-speed read timeout counter

This field sets a period for which the DSI Host keeps the link still, after sending a high-speed read operation. This period is measured in cycles of lanebyteclk. The counting starts when the D-PHY enters the Stop state and causes no interrupts.

30.15.29 DSI Host timeout counter configuration register 2 (DSI_TCCR2)

Address offset: 0x0080

Reset value: 0x0000 0000

Bits 31:16 Reserved, must be kept at reset value.

Bits 15:0 LPRD_TOCNT[15:0] : Low-power read timeout counter

This field sets a period for which the DSI Host keeps the link still, after sending a low-power read operation. This period is measured in cycles of lanebyteclk. The counting starts when the D-PHY enters the Stop state and causes no interrupts.

30.15.30 DSI Host timeout counter configuration register 3 (DSI_TCCR3)

Address offset: 0x0084

Reset value: 0x0000 0000

Bits 31:25 Reserved, must be kept at reset value.

Bit 24 PM : Presp mode

When set to 1, this bit ensures that the peripheral response timeout caused by HSWR_TOCNT is used only once per LTDC frame in command mode, when both the following conditions are met:

• – dpivsync_edpiwms has risen and fallen.
• – Packets originated from LTDC in command mode have been transmitted and its FIFO is empty again.

In this scenario no non-LTDC command requests are sent to the D-PHY, even if there is traffic from generic interface ready to be sent, making it return to stop state. When it does so, PRESP_TO counter is activated and only when it finishes does the controller send any other traffic that is ready.

Bits 23:16 Reserved, must be kept at reset value.

Bits 15:0 HSWR_TOCNT[15:0] : High-speed write timeout counter

This field sets a period for which the DSI Host keeps the link inactive after sending a high-speed write operation. This period is measured in cycles of lanebyteclk . The counting starts when the D-PHY enters the Stop state and causes no interrupts.

30.15.31 DSI Host timeout counter configuration register 4 (DSI_TCCR4)

Address offset: 0x0088

Reset value: 0x0000 0000

Bits 31:16 Reserved, must be kept at reset value.

Bits 15:0 LPWR_TOCNT[15:0] : Low-power write timeout counter

This field sets a period for which the DSI Host keeps the link still, after sending a low-power write operation. This period is measured in cycles of lanebyteclk . The counting starts when the D-PHY enters the Stop state and causes no interrupts.

30.15.32 DSI Host timeout counter configuration register 5 (DSI_TCCR5)

Address offset: 0x008C

Reset value: 0x0000 0000

Bits 31:16 Reserved, must be kept at reset value.

Bits 15:0 BTA_TOCNT[15:0] : Bus-turn-around timeout counter

This field sets a period for which the DSI Host keeps the link still, after completing a bus-turn-around. This period is measured in cycles of lanebyteclk. The counting starts when the D-PHY enters the Stop state and causes no interrupts.

30.15.33 DSI Host clock lane configuration register (DSI_CLCR)

Address offset: 0x0094

Reset value: 0x0000 0000

Bits 31:2 Reserved, must be kept at reset value.

Bit 1 ACR : Automatic clock lane control

This bit enables the automatic mechanism to stop providing clock in the clock lane when time allows.

0: Automatic clock lane control disabled

1: Automatic clock lane control enabled

Bit 0 DPCC : D-PHY clock control

This bit controls the D-PHY clock state:

0: Clock lane is in low-power mode.

1: Clock lane runs in high-speed mode.

30.15.34 DSI Host clock lane timer configuration register (DSI_CLTCR)

Address offset: 0x0098

Reset value: 0x0000 0000

Bits 31:26 Reserved, must be kept at reset value.

Bits 25:16 HS2LP_TIME[9:0] : High-speed to low-power time

This field configures the maximum time that the D-PHY clock lane takes to go from high-speed to low-power transmission measured in lane byte clock cycles.

Bits 15:10 Reserved, must be kept at reset value.

Bits 9:0 LP2HS_TIME[9:0] : Low-power to high-speed time

This field configures the maximum time that the D-PHY clock lane takes to go from low-power to high-speed transmission measured in lane byte clock cycles.

30.15.35 DSI Host data lane timer configuration register (DSI_DLTCR)

Address offset: 0x009C

Reset value: 0x0000 0000

Bits 31:24 HS2LP_TIME[7:0] : High-speed to low-power time

This field configures the maximum time that the D-PHY data lanes take to go from high-speed to low-power transmission measured in lane byte clock cycles.

Bits 23:16 LP2HS_TIME[7:0] : Low-power to high-speed time

This field configures the maximum time that the D-PHY data lanes take to go from low-power to high-speed transmission measured in lane byte clock cycles.

Bit 15 Reserved, must be kept at reset value.

Bits 14:0 MRD_TIME[14:0] : Maximum read time

This field configures the maximum time required to perform a read command in lane byte clock cycles. This register can only be modified when no read command is in progress.

30.15.36 DSI Host PHY control register (DSI_PCTLR)

Address offset: 0x00A0

Reset value: 0x0000 0000

Bits 31:3 Reserved, must be kept at reset value.

Bit 2 CKE : Clock enable

This bit enables the D-PHY clock lane module:

0: D-PHY clock lane module is disabled.

1: D-PHY clock lane module is enabled.

Bit 1 DEN : Digital enable

When set to 0, this bit places the digital section of the D-PHY in the reset state

0: The digital section of the D-PHY is in the reset state.

1: The digital section of the D-PHY is enabled.

Bit 0 Reserved, must be kept at reset value.

30.15.37 DSI Host PHY configuration register (DSI_PCONF _R )

Address offset: 0x00A4

Reset value: 0x0000 0001

Bits 31:16 Reserved, must be kept at reset value.

Bits 15:8 SW_TIME[7:0] : Stop wait time

This field configures the minimum wait period to request a high-speed transmission after the Stop state.

Bits 7:2 Reserved, must be kept at reset value.

Bits 1:0 NL[1:0] : Number of lanes

This field configures the number of active data lanes:

00: One data lane (lane 0)

01: Two data lanes (lanes 0 and 1) - Reset value

Others: Reserved

30.15.38 DSI Host PHY ULPS control register (DSI_PUC _R )

Address offset: 0x00A8

Reset value: 0x0000 0000

Bits 31:4 Reserved, must be kept at reset value.

Bit 3 UEDL : ULPS exit on data lane

• ULPS mode exit on all active data lanes.
• 0: No exit request
• 1: Exit ULPS mode on all active data lane URDL

Bit 2 URDL : ULPS request on data lane

• ULPS mode request on all active data lanes.
• 0: No ULPS request
• 1: Request ULPS mode on all active data lane UECL

Bit 1 UECL : ULPS exit on clock lane

• ULPS mode exit on clock lane.
• 0: No exit request
• 1: Exit ULPS mode on clock lane

Bit 0 URCL : ULPS request on clock lane

• ULPS mode request on clock lane.
• 0: No ULPS request
• 1: Request ULPS mode on clock lane

30.15.39 DSI Host PHY TX triggers configuration register (DSI_PTTCCR)

Address offset: 0x00AC

Reset value: 0x0000 0000

Bits 31:4 Reserved, must be kept at reset value.

Bits 3:0 TX_TRIG[3:0] : Transmission trigger
Escape mode transmit trigger 0-3.
Only one bit of TX_TRIG is asserted at any given time.

30.15.40 DSI Host PHY status register (DSI_PSR)

Address offset: 0x00B0

Reset value: 0x0000 1528

Bits 31:9 Reserved, must be kept at reset value.

Bit 8 UAN1 : ULPS active not lane 1

This bit indicates the status of ulpsactivenot1lane D-PHY signal.

Bit 7 PSS1 : PHY stop state lane 1

This bit indicates the status of phystopstate1lane D-PHY signal.

Bit 6 RUE0 : RX ULPS escape lane 0

This bit indicates the status of rxulpesc0lane D-PHY signal.

Bit 5 UAN0 : ULPS active not lane 0

This bit indicates the status of ulpsactivenot0lane D-PHY signal.

Bit 4 PSS0 : PHY stop state lane 0

This bit indicates the status of phystopstate0lane D-PHY signal.

Bit 3 UANC : ULPS active not clock lane

This bit indicates the status of ulpsactivenotcklane D-PHY signal.

Bit 2 PSSC : PHY stop state clock lane

This bit indicates the status of phystopstatecklane D-PHY signal.

Bit 1 PD : PHY direction

This bit indicates the status of phydirection D-PHY signal.

Bit 0 Reserved, must be kept at reset value.

30.15.41 DSI Host interrupt and status register 0 (DSI_ISR0)

Address offset: 0x00BC

Reset value: 0x0000 0000

Bits 31:21 Reserved, must be kept at reset value.

Bit 20 PE4 : PHY error 4

This bit indicates the LP1 contention error ErrContentionLP1 from lane 0.

Bit 19 PE3 : PHY error 3

This bit indicates the LP0 contention error ErrContentionLP0 from lane 0.

Bit 18 PE2 : PHY error 2

This bit indicates the ErrControl error from lane 0.

Bit 17 PE1 : PHY error 1

This bit indicates the ErrSyncEsc low-power transmission synchronization error from lane 0.

Bit 16 PE0 : PHY error 0

This bit indicates the ErrEsc escape entry error from lane 0.

Bit 15 AE15 : Acknowledge error 15

This bit retrieves the DSI protocol violation from the acknowledge error report.

Bit 14 AE14 : Acknowledge error 14

This bit retrieves the reserved (specific to the device) from the acknowledge error report.

Bit 13 AE13 : Acknowledge error 13

This bit retrieves the invalid transmission length from the acknowledge error report.

Bit 12 AE12 : Acknowledge error 12

This bit retrieves the DSI VC ID Invalid from the acknowledge error report.

Bit 11 AE11 : Acknowledge error 11

This bit retrieves the not recognized DSI data type from the acknowledge error report.

Bit 10 AE10 : Acknowledge error 10

This bit retrieves the checksum error (long packet only) from the acknowledge error report.

Bit 9 AE9 : Acknowledge error 9

This bit retrieves the ECC error, multi-bit (detected, not corrected) from the acknowledge error report.

Bit 8 AE8 : Acknowledge error 8

This bit retrieves the ECC error, single-bit (detected and corrected) from the acknowledge error report.

Bit 7 AE7 : Acknowledge error 7

This bit retrieves the reserved (specific to the device) from the acknowledge error report.

Bit 6 AE6 : Acknowledge error 6

This bit retrieves the false control error from the acknowledge error report.

Bit 5 AE5 : Acknowledge error 5

This bit retrieves the peripheral timeout error from the acknowledge error report.

Bit 4 AE4 : Acknowledge error 4

This bit retrieves the LP transmit sync error from the acknowledge error report.

Bit 3 AE3 : Acknowledge error 3

This bit retrieves the escape mode entry command error from the acknowledge error report.

Bit 2 AE2 : Acknowledge error 2

This bit retrieves the EoT sync error from the acknowledge error report.

Bit 1 AE1 : Acknowledge error 1

This bit retrieves the SoT sync error from the acknowledge error report.

Bit 0 AE0 : Acknowledge error 0

This bit retrieves the SoT error from the acknowledge error report.

30.15.42 DSI Host interrupt and status register 1 (DSI_ISR1)

Address offset: 0x00C0

Reset value: 0x0000 0000

Bits 31:13 Reserved, must be kept at reset value.

Bit 12 GPRXE : Generic payload receive error

This bit indicates that during a generic interface packet read back, the payload FIFO becomes full and the received data is corrupted.

Bit 11 GPRDE : Generic payload read error

This bit indicates that during a DCS read data, the payload FIFO becomes empty and the data sent to the interface is corrupted.

Bit 10 GPTXE : Generic payload transmit error

This bit indicates that during a generic interface packet build, the payload FIFO becomes empty and corrupt data is sent.

Bit 9 GPWRE : Generic payload write error

This bit indicates that the system tried to write a payload data through the generic interface and the FIFO is full. Therefore, the payload is not written.

Bit 8 GCWRE : Generic command write error

This bit indicates that the system tried to write a command through the generic interface and the FIFO is full. Therefore, the command is not written.

Bit 7 LPWRE : LTDC payload write error

This bit indicates that during a DPI pixel line storage, the payload FIFO becomes full and the data stored is corrupted.

Bit 6 EOTPE : EoTp error

This bit indicates that the EoTp packet is not received at the end of the incoming peripheral transmission.

Bit 5 PSE : Packet size error

This bit indicates that the packet size error is detected during the packet reception.

Bit 4 CRCE : CRC error

This bit indicates that the CRC error is detected in the received packet payload.

Bit 3 ECCME : ECC multi-bit error

This bit indicates that the ECC multiple error is detected in a received packet.

Bit 2 ECCSE : ECC single-bit error

This bit indicates that the ECC single error is detected and corrected in a received packet.

Bit 1 TOLPRX : Timeout low-power reception

This bit indicates that the low-power reception timeout counter reached the end and contention is detected.

Bit 0 TOHSTX : Timeout high-speed transmission

This bit indicates that the high-speed transmission timeout counter reached the end and contention is detected.

30.15.43 DSI Host interrupt enable register 0 (DSI_IER0)

Address offset: 0x00C4

Reset value: 0x0000 0000

Bits 31:21 Reserved, must be kept at reset value.

Bit 20 PE4IE : PHY error 4 interrupt enable

This bit enables the interrupt generation on PHY error 4.

0: Interrupt on PHY error 4 disabled

1: Interrupt on PHY error 4 enabled

Bit 19 PE3IE : PHY error 3 interrupt enable

This bit enables the interrupt generation on PHY error 4.

0: Interrupt on PHY error 3 disabled

1: Interrupt on PHY error 3 enabled

Bit 18 PE2IE : PHY error 2 interrupt enable

This bit enables the interrupt generation on PHY error 2.

0: Interrupt on PHY error 2 disabled

1: Interrupt on PHY error 2 enabled

Bit 17 PE1IE : PHY error 1 interrupt enable

This bit enables the interrupt generation on PHY error 1.

0: Interrupt on PHY error 1 disabled

1: Interrupt on PHY error 1 enabled

Bit 16 PE0IE : PHY error 0 interrupt enable

This bit enables the interrupt generation on PHY error 0.

0: Interrupt on PHY error 0 disabled

1: Interrupt on PHY error 0 enabled

Bit 15 AE15IE : Acknowledge error 15 interrupt enable

This bit enables the interrupt generation on acknowledge error 15.

0: Interrupt on acknowledge error 15 disabled

1: Interrupt on acknowledge error 15 enabled

1. Bit 14 AE14IE : Acknowledge error 14 interrupt enable
   This bit enables the interrupt generation on acknowledge error 14.
   0: Interrupt on acknowledge error 14 disabled
   1: Interrupt on acknowledge error 14 enabled
2. Bit 13 AE13IE : Acknowledge error 13 interrupt enable
   This bit enables the interrupt generation on acknowledge error 13.
   0: Interrupt on acknowledge error 13 disabled
   1: Interrupt on acknowledge error 13 enabled
3. Bit 12 AE12IE : Acknowledge error 12 interrupt enable
   This bit enables the interrupt generation on acknowledge error 12.
   0: Interrupt on acknowledge error 12 disabled
   1: Interrupt on acknowledge error 12 enabled
4. Bit 11 AE11IE : Acknowledge error 11 interrupt enable
   This bit enables the interrupt generation on acknowledge error 11.
   0: Interrupt on acknowledge error 11 disabled
   1: Interrupt on acknowledge error 11 enabled
5. Bit 10 AE10IE : Acknowledge error 10 interrupt enable
   This bit enables the interrupt generation on acknowledge error 10.
   0: Interrupt on acknowledge error 10 disabled
   1: Interrupt on acknowledge error 10 enable.
6. Bit 9 AE9IE : Acknowledge error 9 interrupt enable
   This bit enables the interrupt generation on acknowledge error 9.
   0: Interrupt on acknowledge error 9 disabled
   1: Interrupt on acknowledge error 9 enabled
7. Bit 8 AE8IE : Acknowledge error 8 interrupt enable
   This bit enables the interrupt generation on acknowledge error 8.
   0: Interrupt on acknowledge error 8 disabled
   1: Interrupt on acknowledge error 8 enabled
8. Bit 7 AE7IE : Acknowledge error 7 interrupt enable
   This bit enables the interrupt generation on acknowledge error 7.
   0: Interrupt on acknowledge error 7 disabled
   1: Interrupt on acknowledge error 7 enabled
9. Bit 6 AE6IE : Acknowledge error 6 interrupt enable
   This bit enables the interrupt generation on acknowledge error 6.
   0: Interrupt on acknowledge error 6 disabled
   1: Interrupt on acknowledge error 6 enabled
10. Bit 5 AE5IE : Acknowledge error 5 interrupt enable
    This bit enables the interrupt generation on acknowledge error 5.
    0: Interrupt on acknowledge error 5 disabled
    1: Interrupt on acknowledge error 5 enabled
11. Bit 4 AE4IE : Acknowledge error 4 interrupt enable
    This bit enables the interrupt generation on acknowledge error 4.
    0: Interrupt on acknowledge error 4 disabled
    1: Interrupt on acknowledge error 4 enabled

Bit 3 AE3IE : Acknowledge error 3 interrupt enable

This bit enables the interrupt generation on acknowledge error 3.

0: Interrupt on acknowledge error 3 disabled

1: Interrupt on acknowledge error 3 enabled

Bit 2 AE2IE : Acknowledge error 2 interrupt enable

This bit enables the interrupt generation on acknowledge error 2.

0: Interrupt on acknowledge error 2 disabled

1: Interrupt on acknowledge error 2 enabled

Bit 1 AE1IE : Acknowledge error 1 interrupt enable

This bit enables the interrupt generation on acknowledge error 1.

0: Interrupt on acknowledge error 1 disabled

1: Interrupt on acknowledge error 1 enabled

Bit 0 AE0IE : Acknowledge error 0 interrupt enable

This bit enables the interrupt generation on acknowledge error 0.

0: Interrupt on acknowledge error 0 disabled

1: Interrupt on acknowledge error 0 enabled

30.15.44 DSI Host interrupt enable register 1 (DSI_IER1)

Address offset: 0x00C8

Reset value: 0x0000 0000

Bits 31:13 Reserved, must be kept at reset value.

Bit 12 GPRXEIE : Generic payload receive error interrupt enable

This bit enables the interrupt generation on generic payload receive error.

0: Interrupt on generic payload receive error disabled

1: Interrupt on generic payload receive error enabled

Bit 11 GPRDEIE : Generic payload read error interrupt enable

This bit enables the interrupt generation on generic payload read error.

0: Interrupt on generic payload read error disabled

1: Interrupt on generic payload read error enabled

Bit 10 GPTXEIE : Generic payload transmit error interrupt enable

This bit enables the interrupt generation on generic payload transmit error.

0: Interrupt on generic payload transmit error disabled

1: Interrupt on generic payload transmit error enabled

Bit 9 GPWREIE : Generic payload write error interrupt enable

This bit enables the interrupt generation on generic payload write error.

0: Interrupt on generic payload write error disabled

1: Interrupt on generic payload write error enabled

Bit 8 GCWREIE : Generic command write error interrupt enable

This bit enables the interrupt generation on generic command write error.

0: Interrupt on generic command write error disabled

1: Interrupt on generic command write error enabled

Bit 7 LPWREIE : LTDC payload write error interrupt enable

This bit enables the interrupt generation on LTDC payload write error.

0: Interrupt on LTDC payload write error disabled

1: Interrupt on LTDC payload write error enabled

Bit 6 EOTPTEIE : EoTp error interrupt enable

This bit enables the interrupt generation on EoTp error.

0: Interrupt on EoTp error disabled

1: Interrupt on EoTp error enabled

Bit 5 PSEIE : Packet size error interrupt enable

This bit enables the interrupt generation on packet size error.

0: Interrupt on packet size error disabled

1: Interrupt on packet size error enabled

Bit 4 CRCEIE : CRC error interrupt enable

This bit enables the interrupt generation on CRC error.

0: Interrupt on CRC error disabled

1: Interrupt on CRC error enabled

Bit 3 ECCMEIE : ECC multi-bit error interrupt enable

This bit enables the interrupt generation on ECC multi-bit error.

0: Interrupt on ECC multi-bit error disabled

1: Interrupt on ECC multi-bit error enabled

Bit 2 ECCSEIE : ECC single-bit error interrupt enable

This bit enables the interrupt generation on ECC single-bit error.

0: Interrupt on ECC single-bit error disabled

1: Interrupt on ECC single-bit error enabled

Bit 1 TOLPRXIE : Timeout low-power reception interrupt enable

This bit enables the interrupt generation on timeout low-power reception.

0: Interrupt on timeout low-power reception disabled

1: Interrupt on timeout low-power reception enabled

Bit 0 TOHSTXIE : Timeout high-speed transmission interrupt enable

This bit enables the interrupt generation on timeout high-speed transmission .

0: Interrupt on timeout high-speed transmission disabled

1: Interrupt on timeout high-speed transmission enabled

30.15.45 DSI Host force interrupt register 0 (DSI_FIR0)

Address offset: 0x00D8

Reset value: 0x0000 0000

Bits 31:21 Reserved, must be kept at reset value.

Bit 20 FPE4 : Force PHY error 4

Writing one to this bit forces a PHY error 4.

Bit 19 FPE3 : Force PHY error 3

Writing one to this bit forces a PHY error 3.

Bit 18 FPE2 : Force PHY error 2

Writing one to this bit forces a PHY error 2.

Bit 17 FPE1 : Force PHY error 1

Writing one to this bit forces a PHY error 1.

Bit 16 FPE0 : Force PHY error 0

Writing one to this bit forces a PHY error 0.

Bit 15 FAE15 : Force acknowledge error 15

Writing one to this bit forces an acknowledge error 15.

Bit 14 FAE14 : Force acknowledge error 14

Writing one to this bit forces an acknowledge error 14.

Bit 13 FAE13 : Force acknowledge error 13

Writing one to this bit forces an acknowledge error 13.

Bit 12 FAE12 : Force acknowledge error 12

Writing one to this bit forces an acknowledge error 12.

Bit 11 FAE11 : Force acknowledge error 11

Writing one to this bit forces an acknowledge error 11.

Bit 10 FAE10 : Force acknowledge error 10

Writing one to this bit forces an acknowledge error 10.

Bit 9 FAE9 : Force acknowledge error 9

Writing one to this bit forces an acknowledge error 9.

Bit 8 FAE8 : Force acknowledge error 8

Writing one to this bit forces an acknowledge error 8.

Bit 7 FAE7 : Force acknowledge error 7

Writing one to this bit forces an acknowledge error 7.

Bit 6 FAE6 : Force acknowledge error 6

Writing one to this bit forces an acknowledge error 6.

1. Bit 5 FAE5 : Force acknowledge error 5
   Writing one to this bit forces an acknowledge error 5.
2. Bit 4 FAE4 : Force acknowledge error 4
   Writing one to this bit forces an acknowledge error 4.
3. Bit 3 FAE3 : Force acknowledge error 3
   Writing one to this bit forces an acknowledge error 3.
4. Bit 2 FAE2 : Force acknowledge error 2
   Writing one to this bit forces an acknowledge error 2.
5. Bit 1 FAE1 : Force acknowledge error 1
   Writing one to this bit forces an acknowledge error 1.
6. Bit 0 FAE0 : Force acknowledge error 0
   Writing one to this bit forces an acknowledge error 0.

30.15.46 DSI Host force interrupt register 1 (DSI_FIR1)

Address offset: 0x00DC

Reset value: 0x0000 0000

Bits 31:13 Reserved, must be kept at reset value.

1. Bit 12 FGRPXE : Force generic payload receive error
   Writing one to this bit forces a generic payload receive error.
2. Bit 11 FGRDE : Force generic payload read error
   Writing one to this bit forces a generic payload read error.
3. Bit 10 FGPTXE : Force generic payload transmit error
   Writing one to this bit forces a generic payload transmit error.
4. Bit 9 FGPWRE : Force generic payload write error
   Writing one to this bit forces a generic payload write error.
5. Bit 8 FGCWRE : Force generic command write error
   Writing one to this bit forces a generic command write error.
6. Bit 7 FLPWRE : Force LTDC payload write error
   Writing one to this bit forces a LTDC payload write error.
7. Bit 6 FEOTPE : Force EoTp error
   Writing one to this bit forces a EoTp error.
8. Bit 5 FPSE : Force packet size error
   Writing one to this bit forces a packet size error.

• Bit 4 FCRCE : Force CRC error
  Writing one to this bit forces a CRC error.
• Bit 3 FECCME : Force ECC multi-bit error
  Writing one to this bit forces a ECC multi-bit error.
• Bit 2 FECCSE : Force ECC single-bit error
  Writing one to this bit forces a ECC single-bit error.
• Bit 1 FTOLPRX : Force timeout low-power reception
  Writing one to this bit forces a timeout low-power reception.
• Bit 0 FTOHSTX : Force timeout high-speed transmission
  Writing one to this bit forces a timeout high-speed transmission.

30.15.47 DSI Host video shadow control register (DSI_VSCR)

Address offset: 0x0100

Reset value: 0x0000 0000

Bits 31:9 Reserved, must be kept at reset value.

• Bit 8 UR : Update register
  When set to 1, the LTDC registers are copied to the auxiliary registers. After copying, this bit is auto cleared.
  0: No update requested
  1: Register update requested

Bits 7:1 Reserved, must be kept at reset value.

• Bit 0 EN : Enable
  When set to 1, DSI Host LTDC interface receives the active configuration from the auxiliary registers.
  When this bit is set along with the UR bit, the auxiliary registers are automatically updated.
  0: Register update is disabled.
  1: Register update is enabled.

30.15.48 DSI Host LTDC current VCID register (DSI_LCVCIDR)

Address offset: 0x010C

Reset value: 0x0000 0000

Bits 31:2 Reserved, must be kept at reset value.

Bits 1:0 VCID[1:0] : Virtual channel ID

This field returns the virtual channel ID for the LTDC interface.

30.15.49 DSI Host LTDC current color coding register (DSI_LCCCR)

Address offset: 0x0110

Reset value: 0x0000 0000

Bits 31:9 Reserved, must be kept at reset value.

Bit 8 LPE : Loosely packed enable

This bit returns the current state of the loosely packed variant to 18-bit configurations.

0: Loosely packed variant disabled

1: Loosely packed variant enabled

Bits 7:4 Reserved, must be kept at reset value.

Bits 3:0 COLC[3:0] : Color coding

This field returns the current LTDC interface color coding.

0000: 16-bit configuration 1

0001: 16-bit configuration 2

0010: 16-bit configuration 3

0011: 18-bit configuration 1

0100: 18-bit configuration 2

0101: 24-bit

0110 - 1111: reserved

If LTDC interface in command mode is chosen and currently works in the command mode (CMDM=1), then 0110-1111: 24-bit

30.15.50 DSI Host low-power mode current configuration register (DSI_LPMCCR)

Address offset: 0x0118

Reset value: 0x0000 0000

Bits 31:24 Reserved, must be kept at reset value.

Bits 23:16 LPSIZE[7:0] : Largest packet size

This field returns the current size, in bytes, of the largest packet that can fit in a line during VSA, VBP and VFP regions, for the transmission of commands in low-power mode.

Bits 15:8 Reserved, must be kept at reset value.

Bits 7:0 VLPSIZE[7:0] : VACT largest packet size

This field returns the current size, in bytes, of the largest packet that can fit in a line during VACT regions, for the transmission of commands in low-power mode.

30.15.51 DSI Host video mode current configuration register (DSI_VMCCR)

Address offset: 0x0138

Reset value: 0x0000 0000

Bits 31:10 Reserved, must be kept at reset value.

Bit 9 LPCE : Low-power command enable

This bit returns the current command transmission state in low-power mode.

0: Command transmission in low-power mode is disabled.

1: Command transmission in low-power mode is enabled.

Bit 8 FBTAAE : Frame BTA acknowledge enable

This bit returns the current state of request for an acknowledge response at the end of a frame.

0: Acknowledge response at the end of a frame is disabled.

1: Acknowledge response at the end of a frame is enabled.

Bit 7 LPHFE : Low-power horizontal front-porch enable

This bit returns the current state of return to low-power inside the horizontal front-porch (HFP) period when timing allows.
0: Return to low-power inside the HFP period is disabled.
1: Return to low-power inside the HFP period is enabled.

Bit 6 LPHBPE : Low-power horizontal back-porch enable

This bit returns the current state of return to low-power inside the horizontal back-porch (HBP) period when timing allows.
0: Return to low-power inside the HBP period is disabled.
1: Return to low-power inside the HBP period is enabled.

Bit 5 LPVAE : Low-power vertical active enable

This bit returns the current state of return to low-power inside the vertical active (VACT) period when timing allows.
0: Return to low-power inside the VACT is disabled.
1: Return to low-power inside the VACT is enabled.

Bit 4 LPVFPE : Low-power vertical front-porch enable

This bit returns the current state of return to low-power inside the vertical front-porch (VFP) period when timing allows.
0: Return to low-power inside the VFP is disabled.
1: Return to low-power inside the VFP is enabled.

Bit 3 LPVBPE : Low-power vertical back-porch enable

This bit returns the current state of return to low-power inside the vertical back-porch (VBP) period when timing allows.
0: Return to low-power inside the VBP is disabled.
1: Return to low-power inside the VBP is enabled.

Bit 2 LPVSAE : Low-power vertical sync time enable

This bit returns the current state of return to low-power inside the vertical sync time (VSA) period when timing allows.
0: Return to low-power inside the VSA is disabled.
1: Return to low-power inside the VSA is enabled.

Bits 1:0 VMT[1:0] : Video mode type

This field returns the current video mode transmission type:
00: Non-burst with sync pulses
01: Non-burst with sync events
1x: Burst mode

30.15.52 DSI Host video packet current configuration register (DSI_VPCCR)

Address offset: 0x013C

Reset value: 0x0000 0000