Quote Originally Posted by Adrian View Post
I imagined that the programme overhead would mop up 'some' 'ticks' but I was surprised when it ended up at 107 adrift.
You can count that out yourself. Just look at the .lst file, run thru the instructions manually and count them (branches, goto's, returns, retfie, all take 2 cycles, check the datasheet).
If you know that number down to the exact cycle, you should be able to program in a specific frequency and check your oscillator frequency against that with a reasonable amount of accuracy.