On Sat, 5 Jun 2010, David Meiklejohn wrote:

> 
> AM/PM for current and alarm time at stored as single bits within a flag
> register:
> 
> flags       res 1           
>     constant PM=0               ; time AM (0) / PM (1)
>     constant STANDBY=1          ; sleep mode (1)
>     constant DSP_OFF=2          ; display blanked during dimming (1)
>     constant ALM_ON=3           ; alarm on (1)
>     constant ALM_PM=4           ; alarm AM (0) / PM (1)
>     constant ALM_PRS=5          ; debounced ALARM button press (1)
>     constant FAST=6             ; fast time adjust mode (1)
> 

> 
> So finally to the point.  Does anyone know an elegant way to compare (XOR)
> two bits in the same register, using midrange PIC instructions?

	movf	flags,w
	andlw	0x11
	addlw	0x0F		; propergate PM bit to ALM_PM bit and XOR 
				; the new bit with the old bit (at the 
				; ALM_PM bit position)
	andlw	0x10
	btfss	STATUS,Z	; if w == 0 then PM == ALM_PM
	goto	nomatch

match

nomatch


Regards
Sergio Masci
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