by Scott Dattalo
Here's a version that saves the changes and then checks if wither input went high (but doesn't check high to lows):
movf PORTB,w ;get current state xorwf last_in,w ;compare to previous xorwf last_in,f ;save changes andwf last_in,w ;did either go high? andlw (1<<4)||(1<<5) ;only want bits 4 and 5 skpnz goto nolowtohighs ; either bit4 or bit5 went from 0 to 1 ... nolowtohighs
Here's one that does a check and then saves the changes (and will allow you to test high to lows if you want)
movf PORTB,w ;get current state movwf temp xorwf last_in,w ;compare to previous andwf temp,w ;did either go high? andlw (1<<4)||(1<<5) ;only want bits 4 and 5 skpnz goto save changes ; low to high change - do whatever btfsc temp,4 do whatever for bit 4 going high btfsc temp,5 do whatever for bit 5 going high save_changes: movf temp,w xorwf last_in,w xorwf last_in,f
Andrew D. Vassallo says:
Bob Ammerman says: ; compare register "last_inputs" to current PORTB reading ; ; direct computation of ~last_inputs & new_value comf last_inputs,W andwf PORTB,W andlw (1<<4)|(1<<5) skpz goto got_a_0_to_1
|file: /Techref/microchip/math/bit/detchng.htm, 2KB, , updated: 2004/12/6 12:55, local time: 2013/6/20 04:52,
|©2013 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://techref.massmind.org/techref/microchip/math/bit/detchng.htm"> PIC Microcontroller Bit Math Method - Detecting bit changes</A>
|Did you find what you needed?|
Welcome to massmind.org!
Welcome to techref.massmind.org!