01-16-2017 03:55 PM
The Zynq Ultrascale+ real time clock (RTC) on the ZCU102 board is drifting by about 20 minutes per day. This is well beyond the drift that might be attributed to inaccuracy of the 32.768KHz (20ppm) crystal that clocks the RTC.
The RTC contains a calibration register (CALIB_WRITE) that stores the value that is used to generate one second based on the oscillator period. Can anyone tell me how that register value is calculated? It is returning a value of 0x198223, but based on the 32.768KHz clock, I was expecting the value to be 32,768 (0x8000).
Is there anything else that would account for the large drift we are seeing in the RTC?
01-18-2017 10:00 AM
01-18-2017 11:27 AM
Thanks for the suggestion, but I believe the fractional compensation will compensate for minor drifts of 1 or 2 seconds per day. We are seeing drifts of 20 minutes per day.
We are still unable to find any documentation that explains how the calibration register (CALIB_WRITE) is calculated. As I explained in my first post, CALIB_WRITE is returning a value of 0x198223, but based on the 32.768KHz clock, we are expecting the value to be 32,768 (0x8000).
10-23-2018 08:04 AM
07-28-2019 10:47 PM
Are there any updates to this issue?
We have similar problem: The clock on out ZCU102 is skipping one second after every power restart.
So the more we powercycle the board, the RTC is skipping more time.