Calibration Algorithm

Zynq UltraScale+ Device Technical Reference Manual (UG1085)

Document ID
UG1085
Release Date
2022-09-15
Revision
2.3 English

Assuming that the RTC is programmed at time S, then at time T the RTC is showing value R. Each of these time values is the UNIX Epoch time are represented in terms of seconds with respect to a fixed reference, which for UNIX is 00:00:00 on 1/1/1970.

If C and F are defined as:

C = Value of the calibration register (in the seconds calibration field).

F = Value of the calibration register (in the fractional calibration field).

and fractional calibration is enabled, then the actual crystal oscillator frequency is defined in This Equation.

Equation 7-1      Xf = (R–S) × [(C+1) + ((F+1)/16)]/(T–S)

where:

CNEW = Int(Xf) – 1

FNEW = Round((Xf – Int(Xf))×16) – 1