Sections:
; from David Cary: tested on PIC 16F877 ; inc incf count0,f skpnz incf count1,f skpnz incf count2,f ;... {repeat the last two lines for as wide a counter as is needed} ; w is unchanged. ; Status:Z is 1 if and only if counter is now all zeros. ; rest of Status unchanged.
;from Dmitry Kiryashov ;inc movlw 1 addwf count0,F skpnc addwf count1,F ;... {ed: repeat the last two lines for as wide a counter as is needed} ; w is now 1 ; Status:Z and Status:C are 1 if and only if counter is now all zeros. ;dec movlw 1 subwf count0,F skpc subwf count1,F ;... {ed: repeat the last two lines for as wide a counter as is needed} ; w is now 1 ; Status:C is now 0 if and only if counter rolled over and is now all ones ; Status:Z is set if the least significant byte of the counter is zero ; (not necessarily all bytes !) and in certain other cases.
Often we have a value Y (like the index to a circular buffer) that normally increases by 1 each iteration, but that we want to make sure stays in the range 0 <= Y < End. by forcing Y back to zero when it runs off the end of its range.
; if( w <= Y ){ Y = 0; }; ; Y is 8 bits ; by David Cary ; useful for circular buffers. ; Load the upper limit into w  perhaps ; movlw End ; when End is a constant ; movfw End ; when End is a variable subwf Y,w skpnc clrf Y ; now 0 <= Y < End.
[FIXME: 16 bit version ?]
More sophisticated modulus routines are available (typically wrapped up in a routine that calculates both (A/B) and (A MOD B) at once).
Questions:
See also:
file: /Techref/microchip/math/incdec/gp.htm, 2KB, , updated: 2002/9/19 10:55, local time: 2018/5/27 20:44,
owner: DAVMPE62a,

©2018 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions? <A HREF="http://massmind.org/techref/microchip/math/incdec/gp.htm"> PIC Math Increment / Decrement General Purpose</A> 
Did you find what you needed? 
Welcome to massmind.org! 
Welcome to massmind.org! 
.