Figure 38. Synchronization Mode Of The Dmamux Request Line Multiplexer Channel - STMicroelectronics STM32WLEx Reference Manual

RM0461
From this point on, each time the connected DMAMUX request is served by the DMA
controller (a served request is deasserted), the DMAMUX request counter is decremented.
At its underrun, the DMA request counter is automatically loaded with the value in NBREQ
field of the DMAMUX_CxCR register and the input DMA request line is disconnected from
the multiplexer channel x output.
Thus, the number of DMA requests transferred to the multiplexer channel x output following
a detected synchronization event, is equal to the value in NBREQ field, plus one.
Note: The NBREQ field value shall only be written by software when both synchronization enable
bit SE and event generation enable EGE bit of the corresponding multiplexer channel x are
disabled.

Figure 38. Synchronization mode of the DMAMUX request line multiplexer channel

dmamux_syncx
dmamux_req_outx
DMA request counter
Example: DMAMUX_CCRx configured with: NBREQ=4, SE=1, EGE=1, SPOL=01 (rising edge)
Selected
dmamux_reqx
dmamux_evtx
Synchronization event
Input DMA request line connected to output
Selected DMA request line transferred to the output
DMA requests served
4 3 2
Input DMA request line disconnected from output
RM0461 Rev 5
DMA request multiplexer (DMAMUX)
DMA request pending
Not pending
1 0
DMA request counter underrun
DMA request counter auto-reload to NBREQ
4
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