Zybo Z7 clocks and xscutimer

[engrpetero]

I've been making reasonable (good, even) progress with the Vitis IDE and the ZyboZ7.  A question though about clocks on this board and their interface to the Zybo.

I've been using the xscutimer module in interrupt mode.  However, I'm struggling to figure out appropriate values for the TIME_LOAD_VALUE.

If I set it to a pretty high number (hex FFFF FFFF) (dec 4,294,967,295), I see events happen at about 0.8s.  If I set it to 9FFF FFFF (dec 2,684,354,559), I see an event about every 0.5s (they scaled pretty linearly).  Since I believe the timer is just counting this many clock cycles, it seems the clock is way too high - somewhere around  5.3E9 (or I'm not sure how to set this value).  

I've looked at the Zybo reference docs and seem some references to clocks (667Mhz).  I will look further at the Arm9 cortex reference to gain some insight.  But if anyone can help me out, much appreciated.

Peter

[Ana-Maria Balas]

Hello @engrpetero,

Yes, you should check the Technical Reference Manual https://www.xilinx.com/support/documentation/user_guides/ug585-Zynq-7000-TRM.pdf at Chapter 8.

Also more details about the clocks for Zybo are found in the Reference Manual https://reference.digilentinc.com/reference/programmable-logic/zybo-z7/reference-manual#oscillatorsclocks

[Pablo J]

Do you discover how Time load value works?? I'm trying to generate a 20 ms interrupt with a Zybo Z7 and I don't know what value I have to choose. Could you help me??

Thanks :)