PIC Microcontoller Basic Math Inc/Dec Methods

General Purpose from Dmitry Kiryashov
16 bit isosyncronus from Marc Heuler
Best 16 bit from Scott Dattalo
32 bit and detect zero from Dmitry Kiryashov, Rich Leggitt, Andrew Warren, and Scott Dattalo
Inc/Dec Packed BCD by Regulus Berdin
Time Method: Count Seconds, Minutes, and Hours by Andrew Warren

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Microchip instruction set summary (incf, decf, etc..)

From http://www.myke.com/basic.htm: Incrementing/Decrementing "w"

Here are a couple of snippets that will allow you to increment and decrement the "w" register without affecting any file registers if you don't have "addlw"/"sublw" instructions (ie in the case of the low-end processor).
"Reg" can be any register that does not change during the execution of the three instructions. For the low-end parts, any file register can be used because there is no danger of them being updated by an interrupt handler.
To Increment:
 xorlw 0x0FF              ;  Get 1s Complement of Number
  addwf Reg, w             ;  w = Reg + (w^0x0FF)
  subwf Reg, w             ;  w = Reg + ((Reg + (w^0x0FF))^0x0FF) + 1
                           ;  w = w + 1
To decrement, the instructions are re-arranged:
 subwf Reg, w             ;  w = Reg + (2^0x0FF) + 1
  xorlw 0x0FF              ;  Get 1s Complement of Result
  addwf Reg, w             ;  w = w - 1

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