Figure 459. Swpmi Multi Software Buffer Mode Transmission; Reception Procedure - ST STM32L4x6 Reference Manual

Single Wire Protocol Master Interface (SWPMI)
The Software can also read the DMA counter (number of data to transfer) in the DMA
registers in order to retrieve the frame which has already been transferred from the RAM
memory and transmitted. For example, if the software works with 4 transmission buffers, and
if the DMA counter equals 17, it means that two buffers are ready for updating in the RAM
area. This is useful in case several frames are sent before the software can handle the
SWPMI interrupt. If this happens, the software will have to update several buffers.
When there are no more frames to transmit, the user must disable the circular mode in the
DMA module. The transmission will stop at the end of the buffer4 transmission.
If the transmission needs to stop before (for example at the end of buffer2), the user must
set the low significant byte of the first word to 0 in buffer3 and buffer4.
TXDMA bit in the SWPMI_CR register will be cleared by hardware as soon as the number of
data bytes in the payload is read as 0 in the least significant byte of the first word.
40.3.8

Reception procedure

Before starting any frame reception, the user must activate the SWP (refer to
Section 40.3.2: SWP initialization and
Once SWPACT bit is set in the SWPMI_CR register, a RESUME from slave state sets the
SRF flag in the SWPMI_ISR register and automatically enables the SWPMI for the frame
reception.
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Figure 459. SWPMI Multi software buffer mode transmission

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activation.
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