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Meaningless SPI read response from AD5422 (0x000001)

Question asked by aking on Dec 2, 2016
Latest reply on Dec 12, 2016 by aking

While trying to use SPI read back functions with my AD5422 (via J8 on the demo kit EVAL-AD5420/22EBZ), the device responds to every register read query with the same incorrect data regardless of which register is being queried.



Query control register (0x020002), response = (0x000001)

Query status register (0x020000), response = (0x000001)

Query data register (0x020001), response = (0x000001)


I know the device is acknowledging the read command as the SDO line leaves tri-state at the rising edge of LATCH following the read command, as described in the data sheet.


I cannot, however, figure out why the data read back is incorrect, or what 0x000001 is supposed to mean to me.


See the attached scope screen grab for the signals:

Ch1 = Master Out

Ch2 = SCLK

Ch3 = Master In



Any help is appreciated, and I do not mind feeling like a fool when it's something simple.