PIC Microcontoller Math Method

Increment / Decrement

Best 16 bit

;inc
 incf high,f
 incfsz low,f
  decf high,f


A downcounting version;
;dec
  movf    low,f
  skpnz
   decf   high,f
  decf    low,f


on the 18cxxx you can simplify these to:

  infsnz  low,f
   incf   high,f

and
  tstfsz  low,f
   decf   high,f
  decf    low,f

Thanks to Colin Smith for corrections to this page

Al Williams of AWC Says:

Slight typos in the 18F code above for decrement. TSTFSZ doesn't put a result anywhere, so no ,F is required. Also, should be testfsnz but that instruction doesn't exist!
So in fact, you should use the 16F version for decrementing. Also, be aware that the Z flag may be set after this operation but the counter is not zero (just part of it).

Comments:

Decrement Counters at 18F:
decf CounterLow, f
btfss STATUS, C
decf CounterHigh, f
btfss STATUS, C
decf CounterUpper, f
and so on...
Check for Carry-flag in Loops
Loops will execute Counter+1 times.
After Loop's exit, Counter == -1.
+

file: /techref/microchip/math/incdec/best16.htm, 1KB, , updated: 2008/2/20 21:19, local time: 2008/11/21 20:22, owner: AW-AWC-O86,

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