AR# 66568

Zynq UltraScale+ MPSoC - What is the unit of XTime_GetTime()?

Description

I measure software execution time on A53 using XTime_GetTime() in xtime_l.h. What is the unit of this counter value?

Solution

XTime_GetTime() gets the counter value from the Physical Counter (CNTPCT_EL0) in A53. It works at the APU clock frequency.

This logic generates a tick after N clock pulses, where N is as follows:

N=(1/2 APU clock frequency)/100 MHz

100 MHz is a configurable clock that goes to the system timestamp generator in IOU. 

Normally it is 100 MHz after boot but it can be changed using the crl_apb register (Address: 0xFF5E0128).

AR# 66568
Date 03/22/2016
Status Active
Type General Article
Devices