Hi Chris,
The default setting of SPICTL register during SPI Slave Boot is 0x4d22 and the MSBF bit is cleared.
So it is LSB first.
But the Host is sending data in MSB first format.
Hence you have to send the data in LSB first format.
Fpr more details, refer to the SPI Slave Booting chapter in ADSP-214xx Hardware Reference Manual from Pg 915
and also the CCES/VDSP Loader Manual
Regards,
Mahesh