this old code introduces 3us period error

The actual amount there would vary, depending on compiler mode as well as if LED_DLY is a constant or variable - looking at the disassembly would help determine that.

I typically do this:

  TMR0+=-LED_DLY+TMR_ERRORTERM; //where TMR_ERRORTERM is 2 - 4 depending on the disassembly

If you are generating 22us pulses, PWM may be the better way to go.

 

The actual amount there would vary, depending on compiler mode...

.asm *never* varies. Just sayin'...

 

Since the TS is using assembler, that's where the focus needs to be - not another rehash of the C vs assy argument.