Chapter 24 Multichannel Serial Port Interface (McSPI).

www.ti.com Functional Description
24.3.2.10.2 Buffer Almost Full
The bit field MCSPI_XFERLEVEL[AFL] is needed when the buffer is used to receive SPI word from a
slave (MCSPI_CH(I)CONF[FFER] must be set to 1) and register width depends on the generic parameter
FFNBYTE value. It defines the almost full buffer status.
When FIFO pointer reaches this level an interrupt or a DMA request is sent to the CPU to enable system
to read AFL+1 bytes from receive register. Be careful AFL+1 must correspond to a multiple value of
MCSPI_CH(I)CONF[WL].
When DMA is used, the request is de-asserted after the first receive register read.
No new request will be asserted until the system has performed the correct number of read operations
from the buffer.
LH or DMA Read
.
Core Write
Full
Empty
*
Figure 24-19. Buffer Almost Full Level (AFL)
* non-DMA mode only. In DMA mode, the DMA RX request is asserted
to its active level under identical conditions.
(in bytes)
NOTE: SPI_IRQSTATUS register bits are not available in DMA mode. In DMA mode, the
SPIm_DMA_RXn request is asserted on the same conditions as the SPI_IRQSTATUS
RXn_FULL flag.
SPRUH73E–October 2011–Revised May 2012 Multichannel Serial Port Interface (McSPI)
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