About SPI slave on 51422

[Elliot.Chao]

I use the SPI slave function on 51422. When I send a byte(0x31) to 51422 SPI slave from master, 51422 will back a byte (0xAA - DEF byte) to master. Why?

I send 0x31 every 1 seconds, but I always get 0xAA. Why??

[Håkon Alseth]

Hi,

That indicates that an ignored transaction has occurred (DEF register is set to '0xaa' in the SDK example).

1. Have you tried reducing the frequency on the SPIMaster side?
2. Do you always see this issue?
3. Are you sure that your SPIM is within the timing requirements stated for the SPIS module (PS chapter 8.3)?

Best regards Håkon

[Håkon Alseth]

Up to 2MHz is within spec and should be working. Yes, just make sure that both SPI-Master and Slave has the same SPI mode set. It might be that the SPIM clocks out data too fast after CSN is asserted, and adding a delay can work around this.

-H