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AFE7900: AFE7900 Sysref Monitoring

Part Number: AFE7900


We have a custom board that have multiple AFEs and we want to apply Multichip Synchronization steps. So, as first step we are trying to align Sysref and AFE Sampling clock.

After initializing the AFE7900, we continue to send Syref and check Sysref monitor value over the SPI. After that we are trying to set Sysref to 0x1C by reading the Sysref monitorand giving a delay to Sysref until it equals 0x1C. 

The value we read constantly changes between 0x00, 0x1f, 0x1e, 0x1c, 0xf, even when we don't give any delay to Sysref. Shouldn't this value be constant? What is the mistake we made?

Should sysref monitoring be done after or before initiating AFE?

Should the value I need to equalize be 0x1C? 

Should sysref adjustment be done every time card is powered?

Thanks in advance