page 447 of the manual reads that TXSSELx is asserted when bit is set to 0
isn't there a bug in the SDK's fsl_spi.c/irq handler ? see below
Shouldn't the line in blue be
tx_ctrl |= ((uint32_t)SPI_DEASSERT_ALL & ~(uint32_t)SPI_ASSERTNUM_SSEL(handle->sselNum));
This is how the code is written SPI_WriteData() and SPI_MasterTransferBlocking(). See below snapshots
Please ignore this thread; I overlooked the code; I misread SPI_ASSERTNUM_SSEL in the IRQ as SPI_DEASSERTNUM_SSEL. There is no issue.