SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
The TXx_UNDERFLOW event is activated when a channel is enabled and if the MCSPI_TXx register is empty (not updated with new data) when an external master device starts a data transfer with the McSPI (transmit and receive).
When FIFO is enabled, the data emitted while the underflow event is raised is not the last data written in the FIFO but the next data in the FIFO (an old transmitted value or a dummy data in the FIFO has been reset).
TXx_UNDERFLOW indicates an error (data loss) in slave mode.
To avoid having a TXx_UNDERFLOW event at the beginning of a transmission, the TXx_UNDERFLOW event is not activated when no data has been loaded into the MCSPI_TXx register because the channel is enabled.
The MCSPI_IRQSTATUS TXx_UNDERFLOW interrupt status bit must be cleared for interrupt line deassertion (if the event is enabled as the interrupt source).