What is affected by changing the reference clock? Topic is solved

[DemoniacMilk]

I am currently trying to adjust a clock for a serial interface.
As I can only get 25Mhz or 16,6MHz and nothing in between, I am thinking of adjusting the reference clock.
What would be affected by that? I am thinking of timers, is there anything else?

[infiniteimprobability]

The clocks in an xcore are as follows:

Screen Shot 2016-09-19 at 12.51.59.png

(from https://www.xmos.com/download/private/A ... rc1%29.pdf)

Note that XS2 (xcore200) doesn't have standby mode, but the rest is accurate.

Changing the reference clock will affect a lot of stuff - basically anything connected to CLKBLK 0 which by default everything is including timers and ports. You can find out from the code what the speed is using:

PLATFORM_REFERENCE_HZ

and compensate for any use of timers by scaling delays, but slow down the ref clock too much and ports might start behaving differently too. Pretty much all of the software IP written assumes 100MHz ref clock.

You know you can clock a clockblock from the 500MHz clock divided by 2n?

void configure_clock_xcore(clock clk, unsigned char divide);

That may get you closer to what you want without changing ref clock values..

[DemoniacMilk]

Awesome, thank you.
I did not know I can use the system clock to drive ports.