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32 bit and detect zero
Author: Dmitry Kiryashov, Rich Leggitt, Andrew Warren, Scott Dattalo
This code was originally located @ http://www.piclist.com
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; given address of 32 bit little-endian counter in W,
; increment or decrement the counter and return Z set if zero
;Inc32z
;From Dmitry Kiryashov
inc32z:
movwf FSR
clrz
incfsz INDF,F
return
incfsz FSR,F
incfsz INDF,F
return
incfsz FSR,F
incfsz INDF,F
return
incfsz FSR,F
incf INDF,F
return
;Dec32z
;From Rich Leggitt, Andrew Warren, and Dmitry Kiryashov
; 99.2% of the time, this takes 10 cycles w/call
dec32z:
movwf FSR
decfsz INDF,F
goto dec32nz
incf FSR,F
movfw INDF
incf FSR,F
iorwf INDF,W
incf FSR,F
iorwf INDF,W ;get _Z finally
return
dec32nz:
clrz ;set _Z=0
incfsz INDF,W
return
incfsz FSR,F ;doesn't corrupt _Z
decfsz INDF,F
incfsz INDF,W
return
incfsz FSR,F ;...
decfsz INDF,F
incfsz INDF,W
return
incfsz FSR,F ;...
decfsz INDF,F
return
return
;for the 18cxxx instruction set.
;From Scott Dattalo
; 10-16 cycles
dec32:
movwf FSR0L ; the fsr's (three of them) on the 18cxxx
clrf FSR0H ; are 16bits wide
decf POSTINC0,F,1 ;Indirect access that increments the fsr.
bnz dec32nz ;this was bz
;The lsbyte is zero , so we don't need to propogate the borrow
;but we need to see if the higher bytes are zero.
movf POSTINC0,w,1 ;The first byte is zero
iorwf POSTINC0,w,1 ;check the next three
iorwf POSTINC0,w,1
return
dec32nz
;decf on the 18cxxx parts affects C
skpnc
return
decf POSINC0,F,1
skpc
decf POSTINC0,F,1
skpc
decf POSTINC0,F,1
clrz ;was setz
return |
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