SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The event TXx_UNDERFLOW is activated when the channel is enabled and if the MCSPI_TXx register or the FIFO is empty (not updated with new data) when an external master device starts a data transfer with the McSPI (transmit and receive).
The TXx_UNDERFLOW is a harmless warning in master 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. To avoid having a TXx_UNDERFLOW event, the MCSPI_TXx register must seldom be loaded.
The MCSPI_IRQSTATUS TXx_UNDERFLOW interrupt status bit must be cleared for interrupt line deassertion (if the event is enabled as the interrupt source).