SWRU543B January 2019 – June 2025 CC3230S , CC3230SF , CC3235MODS , CC3235MODSF , CC3235S , CC3235SF
In transmit and receive mode, the FIFO can be enabled for write or read request only. The SPI module starts the transfer only when the first write request is released, by writing the SPI_TX register. See Figure 8-17.
This first write request is managed by the IRQ routine or DMA handler.
The sequence varies according to whether word count is used or not (SPI_XFERLEVEL : WCNT ≠ 0 or not). The AEL or AFL values can be different, but they must be a multiple of the word size in the FIFO: 1, 2, or 4 bytes, according to word length.
In these sequences, the transfer to execute has a size of N words. In these sequences, the number of words written or read for each write or read FIFO request are:
If they are not submultiples of N, the last request sizes are:
In these sequences, some soft variables are used:
These variables are initialized before starting the channel.