SWRU543B January 2019 – June 2025 CC3230S , CC3230SF , CC3235MODS , CC3235MODSF , CC3235S , CC3235SF
The bit field MCSPI_XFERLEVEL[AEL] is required when the buffer is used to transmit a SPI word to a slave (MCSPI_CHCONF[FFEW] must be set to 1), and defines the Almost Empty buffer status.
When the FIFO pointer has reached this level, an interrupt or a DMA request is sent to the local host to enable the system to write AEL+1 bytes to the transmit register. AEL+1 must correspond to a multiple value of MCSPI_CHCONF[WL]. When DMA is used, the request is deasserted after the first transmit register write. No new request is asserted again until the system has performed the right number of write accesses. See Figure 8-12.
Figure 8-12 Buffer Almost Empty Level (AEL)