the spelling name of the flag is mixed up with the opposite:
The tooltip for 'SSEL_not_deasserted' is correct, but the text itself is wrong: The flag is set so the text must be 'SSEL_deasserted'.
MCUXpresso 11.0, SDK 2.6.0 for LPC845.
By the way: The macro 'SPI_TXDATCTL_LEN(7)' is ab bit tricky, because this definition is for SPI 8 bit data length. I expected 'SPI_TXDATCTL_LEN(8)' for 8 bit data length and needed a logic analyzer to find out that the LEN field in TXDATCTL is +1 encoded. More precisely: That the macro is +1 encoded as well.