Can you confirm that the SPI in the 21368 can only manage 8-bit or 16-bit data?
How would I connect this to an AD7689 A2D converter, which wants 14 and 15 bit sequences?
Yes the 2136x supports 8, 16 or 32 bit data. For 14 and 15 bit sequences you could use the 16 bit word length with the last bit transmitted as 0 and when you receive 16 bit data you could ignore the last two or one bit based on 14 and 15 bit sequence of your ADC.
Hope this information helps.
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