16. Basic direct memory access controller (BDMA)

16.1 Introduction

The basic direct memory access (BDMA) controller is a bus master and system peripheral.

The BDMA is used to perform programmable data transfers between memory-mapped peripherals and/or memories, upon the control of an off-loaded CPU.

The BDMA controller features a single AHB master architecture.

There are two instances of BDMA, BDMA1 (dedicated to the 8-filter DFSDM) and BDMA2, with 8 channels each.

Each channel is dedicated to managing memory access requests from one or more peripherals. Each BDMA includes an arbiter for handling the priority between DMA requests.

16.2 BDMA main features

• • Single AHB master
• • Peripheral-to-memory, memory-to-peripheral, memory-to-memory and peripheral-to-peripheral data transfers
• • Access to AHB SRAM1/SRAM2 and DFSDM peripheral (BDMA1)
• • Access to SmartRun domain SRAM and AHB/APB peripherals (BDMA2)
• • All BDMA channels independently configurable:
  • – Each channel is associated either with a DMA request signal coming from a peripheral, or with a software trigger in memory-to-memory transfers. This configuration is done by software.
  • – Priority between the requests is programmable by software (4 levels per channel: very high, high, medium, low) and by hardware in case of equality (such as request to channel 1 has priority over request to channel 2).
  • – Transfer size of source and destination are independent (byte, half-word, word), emulating packing and unpacking. Source and destination addresses must be aligned on the data size.
  • – Support of transfers from/to peripherals to/from memory with circular buffer management
  • – Programmable number of data to be transferred: 0 to \( 2^{16} - 1 \)
• • Generation of an interrupt request per channel. Each interrupt request is caused from any of the three DMA events: transfer complete, half transfer, or transfer error.

16.3 BDMA implementation

16.3.1 BDMA1 and BDMA2

BDMA1 and BDMA2 are implemented with the hardware configuration parameters shown in the table below.

Table 96. BDMA1 and BDMA2 implementation

16.3.2 BDMA request mapping

The BDMA2 controller is connected to DMA requests from the AHB/APB peripherals through the DMAMUX2 peripheral.

For the mapping of the different requests, refer to the Section 17.3: DMAMUX implementation .

A channel request x of the BDMA1 is connected to the DFSDM request of the same index x.

16.4 BDMA functional description

16.4.1 BDMA block diagram

The BDMA block diagram is shown in the figure below.

Figure 88. BDMA block diagram

The BDMA controller performs direct memory transfer by sharing the AHB system bus with other system masters. The bus matrix implements round-robin scheduling. DMA requests may stop the CPU access to the system bus for a number of bus cycles, when CPU and BDMA target the same destination (memory or peripheral).

The BDMA2 controller is connected to DMA requests from the AHB/APB peripherals through the DMAMUX2 peripheral.

A channel request x of the BDMA1 is connected to the DFSDM request of the same index x.

According to its configuration through the AHB slave interface, the BDMA controller arbitrates between the DMA channels and their associated received requests. The BDMA controller also schedules the DMA data transfers over the single AHB port master.

The BDMA2 controller generates an interrupt per channel to the interrupt controller and the BDMA1 dedicated to DFSDM generates a single ORed interrupt.

16.4.2 BDMA pins and internal signals

Table 97. BDMA internal input/output signals

16.4.3 BDMA transfers

The software configures the BDMA controller at channel level, in order to perform a block transfer, composed of a sequence of AHB bus transfers.

A BDMA block transfer may be requested from a peripheral, or triggered by the software in case of memory-to-memory transfer.

After an event, the following steps of a single BDMA transfer occur:

1. 1. The peripheral sends a single DMA request signal to the BDMA controller.
2. 2. The BDMA controller serves the request, depending on the priority of the channel associated to this peripheral request.
3. 3. As soon as the BDMA controller grants the peripheral, an acknowledge is sent to the peripheral by the BDMA controller.
4. 4. The peripheral releases its request as soon as it gets the acknowledge from the BDMA controller.
5. 5. Once the request is deasserted by the peripheral, the BDMA controller releases the acknowledge.

The peripheral may order a further single request and initiate another single BDMA transfer.

The request/acknowledge protocol is used when a peripheral is either the source or the destination of the transfer. For example, in case of memory-to-peripheral transfer, the peripheral initiates the transfer by driving its single request signal to the BDMA controller. The BDMA controller reads then a single data in the memory and writes this data to the peripheral.

For a given channel x, a BDMA block transfer consists of a repeated sequence of:

• • a single BDMA transfer, encapsulating two AHB transfers of a single data, over the BDMA AHB bus master:
  • – a single data read (byte, half-word or word) from the peripheral data register or a location in the memory, addressed through an internal current peripheral/memory

address register.

The start address used for the first single transfer is the base address of the peripheral or memory, and is programmed in the BDMA_CPARx or BDMA_CM0/1ARx register.

• – a single data write (byte, half-word or word) to the peripheral data register or a location in the memory, addressed through an internal current peripheral/memory address register.

The start address used for the first transfer is the base address of the peripheral or memory, and is programmed in the BDMA_CPARx or BDMA_CM0/1ARx register.

• • post-decrementing of the programmed BDMA_CNDTRx register
  This register contains the remaining number of data items to transfer (number of AHB 'read followed by write' transfers).

This sequence is repeated until BDMA_CNDTRx is null.

Note: The AHB master bus source/destination address must be aligned with the programmed size of the transferred single data to the source/destination.

16.4.4 BDMA arbitration

The BDMA arbiter manages the priority between the different channels.

When an active channel x is granted by the arbiter (hardware requested or software triggered), a single BDMA transfer is issued (such as a AHB 'read followed by write' transfer of a single data). Then, the arbiter considers again the set of active channels and selects the one with the highest priority.

The priorities are managed in two stages:

• • software: priority of each channel is configured in the BDMA_CCRx register, to one of the four different levels:
  • – very high
  • – high
  • – medium
  • – low
• • hardware: if two requests have the same software priority level, the channel with the lowest index gets priority. For example, channel 2 gets priority over channel 4.

When a channel x is programmed for a block transfer in memory-to-memory mode, re arbitration is considered between each single BDMA transfer of this channel x. Whenever there is another concurrent active requested channel, the BDMA arbiter automatically alternates and grants the other highest-priority requested channel, which may be of lower priority than the memory-to-memory channel.

16.4.5 BDMA channels

Each channel may handle a BDMA transfer between a peripheral register located at a fixed address, and a memory address. The amount of data items to transfer is programmable. The register that contains the amount of data items to transfer is decremented after each transfer.

A DMA channel is programmed at block transfer level.

Programmable data sizes

The transfer sizes of a single data (byte, half-word, or word) to the peripheral and memory are programmable through, respectively, the PSIZE[1:0] and MSIZE[1:0] fields of the BDMA_CCRx register.

Pointer incrementation

The peripheral and memory pointers may be automatically incremented after each transfer, depending on the PINC and MINC bits of the BDMA_CCRx register.

If the incremented mode is enabled (PINC or MINC set to 1), the address of the next transfer is the address of the previous one incremented by 1, 2 or 4, depending on the data size defined in PSIZE[1:0] or MSIZE[1:0]. The first transfer address is the one programmed in the BDMA_CPARx or BDMA_CM0/1ARx register. During transfers, these registers keep the initially programmed value. The current transfer addresses (in the current internal peripheral/memory address register) are not accessible by software.

If the channel x is configured in non-circular mode , no DMA request is served after the last data transfer (once the number of single data to transfer reaches zero). The DMA channel must be disabled in order to reload a new number of data items into the BDMA_CNDTRx register.

Note: If the channel x is disabled, the BDMA registers are not reset. The DMA channel registers (BDMA_CCRx, BDMA_CPARx and BDMA_CM0ARx) retain the initial values programmed during the channel configuration phase.

In circular mode , after the last data transfer, the BDMA_CNDTRx register is automatically reloaded with the initially programmed value. The current internal address registers are reloaded with the base address values from the BDMA_CPARx and BDMA_CM0/1ARx registers.

Channel configuration procedure

The following sequence is needed to configure a DMA channel x:

1. 1. Set the peripheral register address in the BDMA_CPARx register.
   The data is moved from/to this address to/from the memory after the peripheral event, or after the channel is enabled in memory-to-memory mode.
2. 2. Set the memory address in the BDMA_CM0ARx register.
   The data is written to/read from the memory after the peripheral event or after the channel is enabled in memory-to-memory mode.
3. 3. Configure the total number of data to transfer in the BDMA_CNDTRx register.
   After each data transfer, this value is decremented.
4. 4. Configure the parameters listed below in the BDMA_CCRx register:
   • – the channel priority
   • – the data transfer direction
   • – the circular mode
   • – the double-buffer mode
   • – the peripheral and memory incremented mode
   • – the peripheral and memory data size
   • – the interrupt enable at half and/or full transfer and/or transfer error
5. 5. Activate the channel by setting the EN bit in the BDMA_CCRx register.

A channel, as soon as enabled, may serve any BDMA request from the peripheral connected to this channel, or may start a memory-to-memory block transfer.

Note: The two last steps of the channel configuration procedure may be merged into a single access to the BDMA_CCRx register, to configure and enable the channel.

Channel state and disabling a channel

A channel x in active state is an enabled channel (read BDMA_CCRx.EN = 1). An active channel x is a channel that must have been enabled by the software (BDMA_CCRx.EN set to 1) and afterwards with no occurred transfer error (BDMA_ISR.TEIFx = 0). In case there is a transfer error, the channel is automatically disabled by hardware (BDMA_CCRx.EN = 0).

The three following use cases may happen:

• • Suspend and resume a channel

This corresponds to the two following actions:

• – An active channel is disabled by software (writing BDMA_CCRx.EN = 0 whereas BDMA_CCRx.EN = 1).
• – The software enables the channel again (BDMA_CCRx.EN set to 1) without reconfiguring the other channel registers (such as BDMA_CNDTRx, BDMA_CPARx and BDMA_CM0/1ARx).

This case is not supported by the BDMA hardware, that does not guarantee that the remaining data transfers are performed correctly.

• • Stop and abort a channel

If the application does not need any more the channel, this active channel can be disabled by software. The channel is stopped and aborted but the BDMA_CNDTRx register content may not correctly reflect the remaining data transfers versus the aborted source and destination buffer/register.

• • Abort and restart a channel

This corresponds to the software sequence: disable an active channel, then reconfigure the channel and enable it again.

This is supported by the hardware if the following conditions are met:

• – The application guarantees that, when the software is disabling the channel, a DMA data transfer is not occurring at the same time over its master port. For example, the application can first disable the peripheral in DMA mode, in order to ensure that there is no pending hardware DMA request from this peripheral.
• – The software must operate separated write accesses to the same BDMA_CCRx register: First disable the channel. Second reconfigure the channel for a next block transfer including the BDMA_CCRx if a configuration change is needed. There are read-only BDMA_CCRx register fields when BDMA_CCRx.EN=1. Finally enable again the channel.

When a channel transfer error occurs, the EN bit of the BDMA_CCRx register is cleared by hardware. This EN bit can not be set again by software to re-activate the channel x, until the TEIFx bit of the BDMA_CxISR register is set.

Circular mode (in memory-to-peripheral/peripheral-to-memory transfers)

The circular mode is available to handle circular buffers and continuous data flows (such as ADC scan mode). This feature is enabled using the CIRC bit in the BDMA_CCRx register.

Note: The circular mode must not be used in memory-to-memory mode. Before enabling a channel in circular mode ( \( CIRC = 1 \) ), the software must clear the \( MEM2MEM \) bit of the \( BDMA\_CCRx \) register. When the circular mode is activated, the amount of data to transfer is automatically reloaded with the initial value programmed during the channel configuration phase, and the DMA requests continue to be served.

In order to stop a circular transfer, the software needs to stop the peripheral from generating DMA requests (such as quit the ADC scan mode), before disabling the DMA channel. The software must explicitly program the \( BDMA\_CNDTRx \) value before starting/enabling a transfer, and after having stopped a circular transfer.

Memory-to-memory mode

The BDMA channels may operate without being triggered by a request from a peripheral. This mode is called memory-to-memory mode, and is initiated by software.

If the \( MEM2MEM \) bit in the \( BDMA\_CCRx \) register is set, the channel, if enabled, initiates transfers. The transfer stops once the \( BDMA\_CNDTRx \) register reaches zero.

Note: The memory-to-memory mode must not be used in circular mode. Before enabling a channel in memory-to-memory mode ( \( MEM2MEM = 1 \) ), the software must clear the \( CIRC \) bit of the \( BDMA\_CCRx \) register.

Double-buffer mode (in memory-to-peripheral and peripheral-to memory transfers)

The BDMA channels can operate in double-buffer mode.

The difference compared to a regular operation is that the BDMA controller toggles between two memory address pointers at the end of each BDMA transfer, thus accessing two memory areas in an alternate way. This allows the software to access one of the two memory areas while the BDMA controller accesses the other one. The double-buffer mode transfer operates in both directions, so the target memory can be either the source or the destination.

The double-buffer mode is configured by setting both the \( DBM \) and \( CIRC \) bits of the \( BDMA\_CCRx \) register.

Note: The double-buffer mode must not be used in memory-to-memory mode. Before enabling a channel in double-buffer mode ( \( DBM = 1 \) ), the software has to configure appropriately the \( MEM2MEM \) bit ( \( MEM2MEM = 0 \) ).

The steps described below allow the configuration of a BDMA channel x in double-buffer mode:

• • Set the \( DBM \) and \( CIRC \) bits and clear the \( MEM2MEM \) bit of the \( BDMA\_CCRx \) register. The circular mode is then activated for the swap mechanism to occur.
• • Configure the second memory address register \( BDMA\_CM1ARx \) .
• • Continue with the regular channel configuration procedure, and lastly, activate the channel by setting the \( EN \) bit of the \( BDMA\_CCRx \) register. The first BDMA transfer target memory of the corresponding BDMA channel x, is given by the \( CT \) bit of the \( BDMA\_CCRx \) register.

Note: Independently from the value of \( DBM \) bit of the \( BDMA\_CCRx \) register, if \( CT = 1 \) , the memory address pointer for the BDMA transfer is defined by \( BDMA\_CM1ARx \) , and not by \( BDMA\_CM0ARx \) .

Peripheral-to-peripheral mode

Any BDMA channel can operate in peripheral-to-peripheral mode:

• • when the hardware request from a peripheral is selected to trigger the BDMA channel
  This peripheral is the BDMA initiator and paces the data transfer from/to this peripheral to/from a register belonging to another memory-mapped peripheral (this one being not configured in DMA mode).
• • when no peripheral request is selected and connected to the BDMA channel
  The software configures a register-to-register transfer by setting the MEM2MEM bit of the BDMA_CCRx register.

Programming transfer direction, assigning source/destination

The value of the DIR bit of the BDMA_CCRx register sets the direction of the transfer, and consequently, it identifies the source and the destination, regardless the source/destination type (peripheral or memory):

• • DIR = 1 defines typically a memory-to-peripheral transfer. More generally, if DIR = 1:
  • – The source attributes are defined by the BDMA_MARx register, the MSIZE[1:0] field and MINC bit of the BDMA_CCRx register.
    Regardless of their usual naming, these 'memory' register, field and bit are used to define the source peripheral in peripheral-to-peripheral mode.
  • – The destination attributes are defined by the BDMA_PARx register, the PSIZE[1:0] field and PINC bit of the BDMA_CCRx register.
    Regardless of their usual naming, these 'peripheral' register, field and bit are used to define the destination memory in memory-to-memory mode.
• • DIR = 0 defines typically a peripheral-to-memory transfer. More generally, if DIR = 0:
  • – The source attributes are defined by the BDMA_PARx register, the PSIZE[1:0] field and PINC bit of the BDMA_CCRx register.
    Regardless of their usual naming, these 'peripheral' register, field and bit are used to define the source memory in memory-to-memory mode
  • – The destination attributes are defined by the BDMA_MARx register, the MSIZE[1:0] field and MINC bit of the BDMA_CCRx register.
    Regardless of their usual naming, these 'memory' register, field and bit are used to define the destination peripheral in peripheral-to-peripheral mode.

16.4.6 BDMA data width, alignment and endianness

When PSIZE[1:0] and MSIZE[1:0] are not equal, the BDMA controller performs some data alignments as described in the table below.

Table 98. Programmable data width and endian behavior (when PINC = MINC = 1)

Addressing AHB peripherals not supporting byte/half-word write transfers

When the BDMA controller initiates an AHB byte or half-word write transfer, the data are duplicated on the unused lanes of the AHB master 32-bit data bus (HWDATA[31:0]).

When the AHB slave peripheral does not support byte or half-word write transfers and does not generate any error, the BDMA controller writes the 32 HWDATA bits as shown in the two examples below:

• • To write the half-word 0xABCD, the BDMA controller sets the HWDATA bus to 0xABCDABCD with a half-word data size (HSIZE = HalfWord in AHB master bus).
• • To write the byte 0xAB, the BDMA controller sets the HWDATA bus to 0xABABABAB with a byte data size (HSIZE = Byte in the AHB master bus).

Assuming the AHB/APB bridge is an AHB 32-bit slave peripheral that does not take into account the HSIZE data, any AHB byte or half-word transfer is changed into a 32-bit APB transfer as described below:

• • An AHB byte write transfer of 0xB0 to one of the 0x0, 0x1, 0x2 or 0x3 addresses, is converted to an APB word write transfer of 0xB0B0B0B0 to the 0x0 address.
• • An AHB half-word write transfer of 0xB1B0 to the 0x0 or 0x2 addresses, is converted to an APB word write transfer of 0xB1B0B1B0 to the 0x0 address.

16.4.7 BDMA error management

A BDMA transfer error is generated when reading from or writing to a reserved address space. When a BDMA transfer error occurs during a BDMA read or write access, the faulty channel x is automatically disabled through a hardware clear of its EN bit in the corresponding BDMA_CCRx register.

The TEIFx bit of the BDMA_ISR register is set. An interrupt is then generated if the TEIE bit of the BDMA_CCRx register is set.

The EN bit of the BDMA_CCRx register can not be set again by software (channel x re-activated) until the TEIFx bit of the BDMA_ISR register is cleared (by setting the CTEIFx bit of the BDMA_IFCR register).

When the software is notified with a transfer error over a channel which involves a peripheral, the software has first to stop this peripheral in DMA mode, in order to disable any pending or future DMA request. Then software may normally reconfigure both BDMA and the peripheral in DMA mode for a new transfer.

16.5 BDMA interrupts

An interrupt can be generated on a half transfer, transfer complete or transfer error for each DMA channel x. Separate interrupt enable bits are available for flexibility.

Table 99. BDMA interrupt requests

16.6 BDMA registers

Refer to Section 1.2 for a list of abbreviations used in register descriptions.

The BDMA registers have to be accessed by words (32-bit).

16.6.1 BDMA interrupt status register (BDMA_ISR)

Address offset: 0x00

Reset value: 0x0000 0000

Every status bit is cleared by hardware when the software sets the corresponding clear bit or the corresponding global clear bit CGIFx, in the BDMA_IFCR register.

Bit 31 TEIF7 : transfer error (TE) flag for channel 7

0: no TE event

1: a TE event occurred

Bit 30 HTIF7 : half transfer (HT) flag for channel 7

0: no HT event

1: a HT event occurred

Bit 29 TCIF7 : transfer complete (TC) flag for channel 7

0: no TC event

1: a TC event occurred

Bit 28 GIF7 : global interrupt flag for channel 7

0: no TE, HT or TC event

1: a TE, HT or TC event occurred

1. Bit 27 TEIF6 : transfer error (TE) flag for channel 6
   0: no TE event
   1: a TE event occurred
2. Bit 26 HTIF6 : half transfer (HT) flag for channel 6
   0: no HT event
   1: a HT event occurred
3. Bit 25 TCIF6 : transfer complete (TC) flag for channel 6
   0: no TC event
   1: a TC event occurred
4. Bit 24 GIF6 : global interrupt flag for channel 6
   0: no TE, HT or TC event
   1: a TE, HT or TC event occurred
5. Bit 23 TEIF5 : transfer error (TE) flag for channel 5
   0: no TE event
   1: a TE event occurred
6. Bit 22 HTIF5 : half transfer (HT) flag for channel 5
   0: no HT event
   1: a HT event occurred
7. Bit 21 TCIF5 : transfer complete (TC) flag for channel 5
   0: no TC event
   1: a TC event occurred
8. Bit 20 GIF5 : global interrupt flag for channel 5
   0: no TE, HT or TC event
   1: a TE, HT or TC event occurred
9. Bit 19 TEIF4 : transfer error (TE) flag for channel 4
   0: no TE event
   1: a TE event occurred
10. Bit 18 HTIF4 : half transfer (HT) flag for channel 4
    0: no HT event
    1: a HT event occurred
11. Bit 17 TCIF4 : transfer complete (TC) flag for channel 4
    0: no TC event
    1: a TC event occurred
12. Bit 16 GIF4 : global interrupt flag for channel 4
    0: no TE, HT or TC event
    1: a TE, HT or TC event occurred
13. Bit 15 TEIF3 : transfer error (TE) flag for channel 3
    0: no TE event
    1: a TE event occurred
14. Bit 14 HTIF3 : half transfer (HT) flag for channel 3
    0: no HT event
    1: a HT event occurred
15. Bit 13 TCIF3 : transfer complete (TC) flag for channel 3
    0: no TC event
    1: a TC event occurred

1. Bit 12 GIF3 : global interrupt flag for channel 3
   0: no TE, HT or TC event
   1: a TE, HT or TC event occurred
2. Bit 11 TEIF2 : transfer error (TE) flag for channel 2
   0: no TE event
   1: a TE event occurred
3. Bit 10 HTIF2 : half transfer (HT) flag for channel 2
   0: no HT event
   1: a HT event occurred
4. Bit 9 TCIF2 : transfer complete (TC) flag for channel 2
   0: no TC event
   1: a TC event occurred
5. Bit 8 GIF2 : global interrupt flag for channel 2
   0: no TE, HT or TC event
   1: a TE, HT or TC event occurred
6. Bit 7 TEIF1 : transfer error (TE) flag for channel 1
   0: no TE event
   1: a TE event occurred
7. Bit 6 HTIF1 : half transfer (HT) flag for channel 1
   0: no HT event
   1: a HT event occurred
8. Bit 5 TCIF1 : transfer complete (TC) flag for channel 1
   0: no TC event
   1: a TC event occurred
9. Bit 4 GIF1 : global interrupt flag for channel 1
   0: no TE, HT or TC event
   1: a TE, HT or TC event occurred
10. Bit 3 TEIF0 : transfer error (TE) flag for channel 0
    0: no TE event
    1: a TE event occurred
11. Bit 2 HTIF0 : half transfer (HT) flag for channel 0
    0: no HT event
    1: a HT event occurred
12. Bit 1 TCIF0 : transfer complete (TC) flag for channel 0
    0: no TC event
    1: a TC event occurred
13. Bit 0 GIF0 : global interrupt flag for channel 0
    0: no TE, HT or TC event
    1: a TE, HT or TC event occurred

16.6.2 BDMA interrupt flag clear register (BDMA_IFCR)

Address offset: 0x04

Reset value: 0x0000 0000

Setting the global clear bit CGIFx of the channel x in this BDMA_IFCR register, causes the BDMA hardware to clear the corresponding GIFx bit and any individual flag among TEIFx, HTIFx, TCIFx, in the BDMA_ISR register.

Setting any individual clear bit among CTEIFx, CHTIFx, CTCIFx in this BDMA_IFCR register, causes the BDMA hardware to clear the corresponding individual flag and the global flag GIFx in the BDMA_ISR register, provided that none of the two other individual flags is set.

Writing 0 into any flag clear bit has no effect.

Bit 31 CTEIF7 : transfer error flag clear for channel 7

Bit 30 CHTIF7 : half transfer flag clear for channel 7

Bit 29 CTCIF7 : transfer complete flag clear for channel 7

Bit 28 CGIF7 : global interrupt flag clear for channel 7

Bit 27 CTEIF6 : transfer error flag clear for channel 6

Bit 26 CHTIF6 : half transfer flag clear for channel 6

Bit 25 CTCIF6 : transfer complete flag clear for channel 6

Bit 24 CGIF6 : global interrupt flag clear for channel 6

Bit 23 CTEIF5 : transfer error flag clear for channel 5

Bit 22 CHTIF5 : half transfer flag clear for channel 5

Bit 21 CTCIF5 : transfer complete flag clear for channel 5

Bit 20 CGIF5 : global interrupt flag clear for channel 5

Bit 19 CTEIF4 : transfer error flag clear for channel 4

Bit 18 CHTIF4 : half transfer flag clear for channel 4

Bit 17 CTCIF4 : transfer complete flag clear for channel 4

Bit 16 CGIF4 : global interrupt flag clear for channel 4

Bit 15 CTEIF3 : transfer error flag clear for channel 3

Bit 14 CHTIF3 : half transfer flag clear for channel 3

Bit 13 CTCIF3 : transfer complete flag clear for channel 3

• Bit 12 CGIF3 : global interrupt flag clear for channel 3
• Bit 11 CTEIF2 : transfer error flag clear for channel 2
• Bit 10 CHTIF2 : half transfer flag clear for channel 2
• Bit 9 CTCIF2 : transfer complete flag clear for channel 2
• Bit 8 CGIF2 : global interrupt flag clear for channel 2
• Bit 7 CTEIF1 : transfer error flag clear for channel 1
• Bit 6 CHTIF1 : half transfer flag clear for channel 1
• Bit 5 CTCIF1 : transfer complete flag clear for channel 1
• Bit 4 CGIF1 : global interrupt flag clear for channel 0
• Bit 3 CTEIF0 : transfer error flag clear for channel 0
• Bit 2 CHTIF0 : half transfer flag clear for channel 0
• Bit 1 CTCIF0 : transfer complete flag clear for channel 0
• Bit 0 CGIF0 : global interrupt flag clear for channel 0

16.6.3 BDMA channel x configuration register (BDMA_CCRx)

Address offset: 0x08 + 0x14 * x, (x = 0 to 7)

Reset value: 0x0000 0000

The register fields/bits CT, DBM, MEM2MEM, PL[1:0], MSIZE[1:0], PSIZE[1:0], MINC, PINC, and DIR are read-only when EN = 1.

The states of MEM2MEM and CIRC bits must not be both high at the same time.

Bits 31:17 Reserved, must be kept at reset value.

Bit 16 CT : current target memory of DMA transfer in double-buffer mode

This bit is toggled by hardware at the end of each channel transfer in double-buffer mode.

0: memory 0 (addressed by the BDMA_CM0AR pointer)

1: memory 1 (addressed by the BDMA_CM1AR pointer)

Note: this bit is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is read-only when the channel is enabled (EN = 1).

Bit 15 DBM : double-buffer mode

This bit must be set only in memory-to-peripheral and peripheral-to-memory transfers (MEM2MEM=0). The CIRC bit must also be set in double buffer mode.

0: disabled (no memory address switch at the end of the BDMA transfer)

1: enabled (memory address switched at the end of the BDMA transfer)

Note: this bit is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is not read-only when the channel is enabled (EN = 1).

Bit 14 MEM2MEM : memory-to-memory mode

0: disabled

1: enabled

Note: this bit is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is read-only when the channel is enabled (EN = 1).

Bits 13:12 PL[1:0] : priority level

00: low

01: medium

10: high

11: very high

Note: this field is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is read-only when the channel is enabled (EN = 1).

Bits 11:10 MSIZE[1:0] : memory size

Defines the data size of each DMA transfer to the identified memory.

In memory-to-memory mode, this field identifies the memory source if DIR = 1 and the memory destination if DIR = 0.

In peripheral-to-peripheral mode, this field identifies the peripheral source if DIR = 1 and the peripheral destination if DIR = 0.

00: 8 bits

01: 16 bits

10: 32 bits

11: reserved

Note: this field is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is read-only when the channel is enabled (EN = 1).

Defines the data size of each DMA transfer to the identified peripheral.

In memory-to-memory mode, this field identifies the memory destination if DIR = 1 and the memory source if DIR = 0.

In peripheral-to-peripheral mode, this field identifies the peripheral destination if DIR = 1 and the peripheral source if DIR = 0.

00: 8 bits

01: 16 bits

10: 32 bits

11: reserved

Note: this field is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is read-only when the channel is enabled (EN = 1).

Defines the increment mode for each DMA transfer to the identified memory.

In memory-to-memory mode, this field identifies the memory source if DIR = 1 and the memory destination if DIR = 0.

In peripheral-to-peripheral mode, this field identifies the peripheral source if DIR = 1 and the peripheral destination if DIR = 0.

0: disabled

1: enabled

Note: this bit is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is read-only when the channel is enabled (EN = 1).

Defines the increment mode for each DMA transfer to the identified peripheral.

In memory-to-memory mode, this field identifies the memory destination if DIR = 1 and the memory source if DIR = 0.

In peripheral-to-peripheral mode, this field identifies the peripheral destination if DIR = 1 and the peripheral source if DIR = 0.

0: disabled

1: enabled

Note: this bit is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is read-only when the channel is enabled (EN = 1).

0: disabled

1: enabled

Note: this bit is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is not read-only when the channel is enabled (EN = 1).

This bit must be set only in memory-to-peripheral and peripheral-to-memory modes.

0: read from peripheral

• – Source attributes are defined by PSIZE and PINC, plus the BDMA_CPARx register. This is still valid in a memory-to-memory mode.
• – Destination attributes are defined by MSIZE and MINC, plus the BDMA_CM0/1ARx register. This is still valid in a peripheral-to-peripheral mode.

1: read from memory

• – Destination attributes are defined by PSIZE and PINC, plus the BDMA_CPARx register. This is still valid in a memory-to-memory mode.
• – Source attributes are defined by MSIZE and MINC, plus the BDMA_CM0/1ARx register. This is still valid in a peripheral-to-peripheral mode.

Note: this bit is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is read-only when the channel is enabled (EN = 1).

0: disabled

1: enabled

Note: this bit is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is not read-only when the channel is enabled (EN = 1).

0: disabled

1: enabled

Note: this bit is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is not read-only when the channel is enabled (EN = 1).

0: disabled

1: enabled

Note: this bit is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is not read-only when the channel is enabled (EN = 1).

When a channel transfer error occurs, this bit is cleared by hardware. It can not be set again by software (channel x re-activated) until the TEIFx bit of the BDMA_ISR register is cleared (by setting the CTEIFx bit of the BDMA_IFCR register).

0: disabled

1: enabled

Note: this bit is set and cleared by software.

16.6.4 BDMA channel x number of data to transfer register (BDMA_CNDTRx)

Address offset: \( 0x0C + 0x14 * x \) , ( \( x = 0 \) to \( 7 \) )

Reset value: \( 0x0000\ 0000 \)

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

Bits 15:0 NDT[15:0] : number of data to transfer ( \( 0 \) to \( 2^{16} - 1 \) )

This field is updated by hardware when the channel is enabled:

• – It is decremented after each single BDMA 'read followed by write' transfer, indicating the remaining amount of data items to transfer.
• – It is kept at zero when the programmed amount of data to transfer is reached, if the channel is not in circular mode ( \( CIRC = 0 \) in the BDMA_CCRx register).
• – It is reloaded automatically by the previously programmed value, when the transfer is complete, if the channel is in circular mode ( \( CIRC = 1 \) ).

If this field is zero, no transfer can be served whatever the channel status (enabled or not).

Note: this field is set and cleared by software.

It must not be written when the channel is enabled ( \( EN = 1 \) ).

It is read-only when the channel is enabled ( \( EN = 1 \) ).

16.6.5 BDMA channel x peripheral address register (BDMA_CPARx)

Address offset: \( 0x10 + 0x14 * x \) , ( \( x = 0 \) to \( 7 \) )

Reset value: \( 0x0000\ 0000 \)

Bits 31:0 PA[31:0] : peripheral address

It contains the base address of the peripheral data register from/to which the data is read/written.

When PSIZE[1:0] = 01 (16 bits), bit 0 of PA[31:0] is ignored. Access is automatically aligned to a half-word address.

When PSIZE = 10 (32 bits), bits 1 and 0 of PA[31:0] are ignored. Access is automatically aligned to a word address.

In memory-to-memory mode, this register identifies the memory destination address if DIR = 1 and the memory source address if DIR = 0.

In peripheral-to-peripheral mode, this register identifies the peripheral destination address if DIR = 1 and the peripheral source address if DIR = 0.

Note: this register is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is not read-only when the channel is enabled (EN = 1).

16.6.6 BDMA channel x memory 0 address register (BDMA_CM0ARx)

Address offset: 0x14 + 0x14 * x, (x = 0 to 7)

Reset value: 0x0000 0000

Bits 31:0 MA[31:0] : peripheral address

It contains the base address of the memory from/to which the data is read/written.

When MSIZE[1:0] = 01 (16 bits), bit 0 of MA[31:0] is ignored. Access is automatically aligned to a half-word address.

When MSIZE = 10 (32 bits), bits 1 and 0 of MA[31:0] are ignored. Access is automatically aligned to a word address.

In memory-to-memory mode, this register identifies the memory source address if DIR = 1 and the memory destination address if DIR = 0.

In peripheral-to-peripheral mode, this register identifies the peripheral source address if DIR = 1 and the peripheral destination address if DIR = 0.

Note: this register is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is not read-only when the channel is enabled (EN = 1).

16.6.7 BDMA channel x memory 1 address register (BDMA_CM1ARx)

Address offset: 0x18 + 0x14 * x, (x = 0 to 7)

Reset value: 0x0000 0000

Bits 31:0 MA[31:0] : peripheral address

It contains the base address of the memory from/to which the data is read/written.

When MSIZE[1:0] = 01 (16 bits), bit 0 of MA[31:0] is ignored. Access is automatically aligned to a half-word address.

When MSIZE = 10 (32 bits), bits 1 and 0 of MA[31:0] are ignored. Access is automatically aligned to a word address.

In memory-to-memory mode, this register identifies the memory source address if DIR = 1 and the memory destination address if DIR = 0.

In peripheral-to-peripheral mode, this register identifies the peripheral source address if DIR = 1 and the peripheral destination address if DIR = 0.

Note: this register is set and cleared by software.

It must not be written when the channel is enabled (EN = 1).

It is not read-only when the channel is enabled (EN = 1).

16.6.8 BDMA register map

The table below gives the BDMA register map and reset values.

Table 100. BDMA register map and reset values

Table 100. BDMA register map and reset values (continued)

Table 100. BDMA register map and reset values (continued)