Bpsk Framing; Sub-Ghz Radio Data Buffer; Figure 14. Sub-Ghz Ram Data Buffer Operation - STMicroelectronics STM32WL5 Series Reference Manual

RM0453
5.5.7

BPSK framing

The BPSK packet framing is used with the BPSK modem. The BPSK packet framing can be
configured by Set_PacketParams() command and allows the total frame length
definition. The full packet (preamble, synch word, device id to CRC) must be provided in the
transmit data buffer.
5.6

Sub-GHz radio data buffer

The sub-GHz radio uses a 256-byte RAM data buffer that is accessible by the CPU through
the SUBGHZSPI interface in all sub-GHz radio operating modes except Sleep and
Deep-Sleep. The RAM data buffer is cleared in Deep-Sleep mode, optionally retained in
Sleep mode and always retained in all other modes. In Sleep and Deep-Sleep modes, the
TxBaseAddr and RxBaseAddr values are lost. In order to retrieve data after Sleep mode
retention, the default values must be used (TxBaseAddr = 0x80 and RxBaseAddr = 0x00),
or RxPayloadLength and RxBufferPointer must be stored in the CPU memory.
On die revision Y and later, the PayloadLength can be updated during transmission. This
capability allows the support of long packets.
On previous die revisions, the PayloadLength is fixed (latched in the radio) after a SetTx()
command.
The RAM data buffers are fully configurable. They allow access to the transmit data buffer
and the last receive data buffer. The RAM data buffer organization is depicted in the figure
below.
TxBaseAddr + RTxPayloadLength
The RAM data buffer is accessed by Write_Buffer() and Read_Buffer()commands.
The offset parameter defines the address in the SRAM data buffer. To read the first byte

Figure 14. Sub-GHz RAM data buffer operation

CPU side
address 0xFF
Write_Buffer()
TxBaseAddr
Read_Buffer()
RxBaseAddr
address 0x00
RAM data
buffer
TxBufferPointer
Transmit
data buffer
Receive
data buffer
Last received
payload
RM0453 Rev 5
Sub-GHz radio (SUBGHZ)
Sub-GHz radio side
RxBufferPointer + RTxPayloadLength
RxBufferPointer
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