10. PTA converter (PTACONV)

10.1 PTACONV introduction

The PTA converter is used to convert the PTA information coming from the 2.4 GHz RADIO into the PTA protocol used on the PTA controller GPIOs.

This IP is available only on STM32WBA55xx and STM32WBA54xx devices.

10.2 PTACONV main features

• • Based on IEEE802.15.2 standard
• • Supports both grant and deny signaling
• • Supports from 1- to 4-wire protocols
• • Programmable transmit/receive PTA_STATUS polarity
• • Programmable priority polarity
• • Programmable grant polarity
• • Programmable active polarity
• • Programmable PTA_ACTIVE timing
• • Programmable PTA_STATUS time-multiplexed priority timing
• • Programmable transmit packet abort

10.3 PTACONV functional description

The PTA converter adapts the PTA protocol to the various external PTA controllers. It supports a grant or deny signaling on the PTA_GRANT signal, and the following protocols:

• • 1-wire PTA_ACTIVE
• • 2-wire PT_ACTIVE and PTA_GRANT
• • 3-wire PTA_ACTIVE, PTA_GRANT and time-multiplexed PTA_STATUS
• • 4-wire PTA_ACTIVE, PTA_GRANT, PTA_PRIORITY and PTA_STATUS

When the request to cease an ongoing transmission occurs near the end of the 2.4 GHz RADIO packet, PTA_ACTIVE is deactivated at the end of the packet, before the expiration of T4.

10.3.1 PTACONV block diagram

Figure 24 shows the PTA converter block diagram and the interface to the 2.4 GHz RADIO.

The PTACONV is clocked by the 2.4 GHz RADIO kernel clock, independently from the hclk for the AHB interface used to access the PTACONV configuration registers.

10.3.2 PTACONV pins and internal signals

Table 80. 2.4 PTACONV input/output pins

Table 81. PTACONV internal input/output signals

Table 81. PTACONV internal input/output signals (continued)

10.3.3 PTACONV protocols

The PTA grant protocol, the PTA deny protocol, and the 3-wire PTA_STATUS time-multiplexed priority and status transmit/receive information are detailed in this section.

PTA grant protocol

The 4-wire PTA grant protocol uses PTA_ACTIVE, PTA_STATUS, PTA_PRIORITY, and PTA_GRANT signals, as shown in Figure 25.

Figure 25. 4-wire PTA grant protocol

Timing parameters:

• • T1 is the time for the PTA_ACTIVE signal to request the medium before the start of the 2.4 GHz RADIO packet transfer.
• • T2 is the time before the start of the 2.4 GHz RADIO packet transfer, during which the PTA_GRANT is stable.
• • T4 is the delay time to cease an ongoing 2.4 GHz RADIO packet transmission and to deactivate PTA_ACTIVE.

Time instances:

• • t1: the request signal is activated before the 2.4 GHz RADIO packet transfer. For transmit and receive master packets t1 is also the time PTA_ACTIVE is activated.
• • t2: PTA_GRANT signal is stable.
• • t3 start of the 2.4 GHz RADIO packet transfer.
• • t3.1: the 2.4 GHz RADIO packet transfer is denied, and PTA_ACTIVE is deactivated. The external PTA controller can remove the PTA_GRANT as well.
• • t4: indicates the end of the 2.4 GHz RADIO packet and the deactivation of the PTA_ACTIVE signal when active. The external PTA controller can remove the PTA_GRANT as well.
• • t5: PTA_GRANT goes to deny and requests to cease the ongoing packet transmission.
• • t5.1: indicates that the ongoing packet is aborted and PTA_ACTIVE signal is deactivated. Abortion of the transmit packet can be disabled with register bit. ABORTDIS, in this case the ngrant signal stays low until the end of the transmit packet.
• • t6: the receive packet has been detected and used for slave receive packets to activate the PTA_ACTIVE signal.
• • t7: PTA_GRANT is stable.

Receive packets are always granted and reception always proceeds. Receive packets use the PTA protocol to request the reservation of the medium for high priority receive packets.

PTA deny protocol

The PTA deny protocol uses PTA_ACTIVE, PTA_STATUS, PTA_PRIORITY and PTA_DENY signals, as shown in Figure 26.

Figure 26. 4-wire PTA deny protocol

Timing parameters:

• • T1 is the time for the PTA_ACTIVE signal to request the medium before the start of the 2.4 GHz RADIO packet transfer.
• • T2 is the time before the start of the 2.4 GHz RADIO packet transfer, during which the PTA_GRANT is stable.

Time instances:

• • t1: the request signal is activated before the 2.4 GHz RADIO packet transfer. For transmit and receive master packets t1 is also the time PTA_ACTIVE is activated.
• • t2: PTA_GRANT signal is stable.
• • t3: start of the 2.4 GHz RADIO packet transfer.
• • t3.1: a 2.4 GHz RADIO packet transfer is denied and the PTA_ACTIVE is deactivated. The external PTA controller too can remove the PTA_GRANT.
• • t4: indicates the end of the 2.4 GHz RADIO packet and the deactivation of the PTA_ACTIVE signal when active. The external PTA controller too can remove the PTA_GRANT.
• • t5: PTA_GRANT goes to deny and requests to cease the ongoing packet transmission.
• • t5.1: indicates that the ongoing packet is aborted and the PTA_ACTIVE signal is deactivated. Abortion of the transmit packet can be disabled with register bit ABORTDIS, in this case the deny signal stays high until the end of the transmit packet.
• • t6: the receive packet has been detected and used for slave receive packets to activate the PTA_ACTIVE signal.
• • t7: PTA_GRANT is stable.

Receive packets are always granted and reception always proceeds. Receive packets use the PTA protocol to request the reservation of the medium for high priority receive packets.

3-wire time shared PTA_STATUS

The 3-wire PTA protocol does not use the PTA_PRIORITY signal. The priority and transmit receive packet status information is time-multiplexed on the PTA_STATUS signal, as shown in Figure 27.

Figure 27. 3-wire time-multiplexed PTA_STATUS

Timing parameters:

• • T1 is the time for the PTA_ACTIVE to request the medium before the start of the 2.4 GHz RADIO packet transfer.
• • T2 is the time before the start of the 2.4 GHz RADIO packet transfer during which the PTA_GRANT is stable.
• • T3 is the time the priority is time-multiplexed on the PTA_STATUS signal.

Time instances:

• • t1: the request signal is activated before the 2.4 GHz RADIO packet transfer. For transmit and receive master packets it is also the time PTA_ACTIVE is activated. Priority information is time-multiplexed on the PTA_STATUS signal.
• • t1.1: the transmit or receive status is time-multiplexed on the PTA_STATUS signal.
• • t2: PTA_GRANT signal is stable.
• • t3: start of the 2.4 GHz RADIO packet transfer.

PTA timing parameters

Table 82. 2.4 PTACONV timing parameters

10.3.4 PTACONV interface with the 2.4 GHz RADIO

The 2.4 GHz RADIO provides the following signals:

• • ptaconv_active:
  • – activated with a T1 setup time before the start of the packet. This is before:
    • > the PA ramping for transmit packet
    • > the start of the receive window for receive packets
  • – deactivated at the end of the scheduled packet. This is after:
    • > the PA has ramped down for transmit packets
    • > the last receive packet bit has been received, or the at the end of the review window when no packet detected
• • ptaconv_priority: signaling 0 for low priority packets, 1 for high priority packets
• • ptaconv_status_txrx: signaling 0 for receive packets, 1 for transmit packets
• • ptaconv_status_ms: signaling 0 for master packets, 1 for slave packets
• • ptaconv_packet_detect: receive packet (access code) detect indication
• • ptaconv_ngrant: active low grant signal
  • – to be sampled during the valid window T2 to determine if a packet transmission is granted or denied
  • – monitored during the transmit packet to cease transmission upon the reception of a deny

10.4 Low-power modes

The PTACONV supports operation in low power modes, as detailed in the following table.

10.5 PTACONV registers

10.5.1 PTACONV active control register (PTACONV_ACTCR)

Address offset: 0x000

Reset value: 0x0005 0014

Access: no wait state; word, half-word and byte access

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

Bit 20 ABORTDIS : Disable PTA_ACTIVE deny to abort an ongoing transmission

• Set and cleared by software to define if PTA_ACTIVE will abort an ongoing transmission.
• 0: PTA_ACTIVE deny aborts an ongoing transmission
• 1: PTA_ACTIVE deny does not abort an ongoing transmission

Bits 19:16 TABORT[3:0] : PTA_ACTIVE delay to cease an ongoing transmission in \( \mu\text{s} \)

• Set and cleared by software to define transmit packet abort delay and signaling on PTA_ACTIVE.
• 0x5 to 0xA: transmit packet PTA_ACTIVE abort delay time: \( T_{4\_PTA} = \text{TABORT} \times 1 \mu\text{s} \)
• Others: reserved

Bit 15 ACTPOL : PTA_ACTIVE polarity

• Set and cleared by software to define PTA_ACTIVE signal polarity.
• 0: PTA_ACTIVE active high
• 1: PTA_ACTIVE active low

Bits 14:8 Reserved, must be kept at reset value.

Bits 7:0 TACTIVE[7:0] : PTA_ACTIVE setup time in \( \mu\text{s} \)

• Set and cleared by software to define PTA_ACTIVE setup time.
• 0x14 to 0x96: PTA_ACTIVE setup time: \( T_{1\_PTA} = \text{TACTIVE} \times 1 \mu\text{s} \)
• Others: reserved

10.5.2 PTACONV priority control register (PTACONV_PRICR)

Address offset: 0x004

Reset value: 0x0000 000A

Access: no wait state; word, half-word and byte access

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

Bit 15 PRIPOL : Priority polarity

Set and cleared by software to define PTA_PRIOROITY and time-multiplexed priority on PTA_STATUS signal polarity.

0: priority on PTA_PRIORITY or PTA_STATUS not inverted

1: inverted priority on PTA_PRIORITY or PTA_STATUS

Bits 14:5 Reserved, must be kept at reset value.

Bits 4:0 TPRIORITY[4:0] : Priority valid time in \( \mu\text{s} \)

Set and cleared by software to define PTA_STATUS signal priority valid time.

0x00: no time-multiplexed priority information on PTA_STATUS

0x08 to 0x14: priority information multiplexed on PTA_STATUS with valid time:

\( T_{3\_PTA} = \text{TPRIORITY} \times 1 \mu\text{s} \)

Others: reserved

10.5.3 PTACONV control register (PTACONV_CR)

Address offset: 0x008

Reset value: 0x0000 0000

Access: no wait state; word, half-word and byte access

Bit 31 GRANTPOL : PTA_GRANT polarity

Set and cleared by software to define PTA_GRANT signal polarity.

0: PTA_GRANT active low

1: PTA_GRANT active high

Bits 30:16 Reserved, must be kept at reset value.

Bit 15 TXRXPOL : PTA_STATUS transmit and receive polarity

Set and cleared by software to define PTA_STATUS signal polarity for transmit and receive information.

0: PTA_STATUS receive = 0, transmit = 1

1: PTA_STATUS receive = 1, transmit = 0

Bits 14:0 Reserved, must be kept at reset value.

10.5.4 PTACONV register map

Table 84. PTACONV register map and reset values

Refer to Section 2.3 for the register boundary addresses.