SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The MCSPI_XFERLEVEL[7:0] AEL bit field is needed when the buffer is used to transmit an SPI word to a slave (the MCSPI_CHxCONF[27] FFEW bit must be set to 1). It defines the almost-empty buffer status. See Figure 26-95.
When the FIFO pointer does not reach this level, an interrupt or a DMA request is sent to the MPU to enable the system to write AEL + 1 bytes to the transmit register.
AEL + 1 must correspond to a multiple value of the MCSPI_CHxCONF[11:7] WL bit field.
When DMA is used, the request is deasserted after the first transmit register write.
No new request is asserted again as long as the system has not performed the correct number of write accesses.
The MCSPI_IRQSTATUS register bits are not available in DMA mode. In DMA mode, the SPIm_DMA_TXx request is asserted on the same conditions as the MCSPI_IRQSTATUS TXx_EMPTY flag.