From Scott Dattalo
;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,fThanks 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).
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.+
decf16 macro file ; Decrease 16bit file, Z flag correct movf file,f ; Check low byte skpnz ; Low byte zero? decf file+1,f ; Yes, need to decrement HB as well decf file,f ; Decrement low byte skpnz ; Skip if no further checks needed to set Z movf file+1, f ; LB is zero, now check HB endm+
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<A HREF="http://www.piclist.com/Techref/Microchip/math/incdec/best16.htm"> PIC Math Increment / Decrement Best 16Bit</A>
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