The SigmaDSP products (and most devices from Analog Devices with SPI ports) use SPI Mode 3, in which CPOL = 1 and CPHA = 1.
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This FAQ was generated from the following discussion: Looking for detailed info on adau1961 spi protocol
Yes, that's correct. The uC should use mode 3.
Should SPI mode of uC set to "mode 3" for SPI communication with AD1940?