On Sat, 14 Jan 2012, Bob Blick wrote:

> I have an existing small PIC project that produces an output on one pin
> based on the high bit of a register. In order to save an external
> inverter, I'd like to also output the complement on another pin. For the
> sake of argument let's say it is an oscillator that blinks an LED or
> drives a transducer.
>
> The target is a 16F627A and any pins are fair game, but glitches are not
> OK to the two pins, so no math or rotates directly on the ports.
>
> It is OK to do anything to any of the other pins.
>
> It is OK for there to be a little latency, and either port A or port B
> is OK. Or even both ports, though I don't see how that could get any
> faster.
>
> Here's the fastest thing I could come up with:
>
> movlw 0x55
> btfss bigreg,7
> movlw 0xAA
> movwf PORTA
>
> This is almost fast enough, if I could shave an instruction off one of
> the two conditions it would be enough for me.
>
> Any suggestions?
>
> Thanks, Bob


bcf	STATUS,C
rrf	bigreg,w
addlw	0x40
movwf	PORTA

if you can ensure that the carry flag is in a known state as a side effect=
=20
of previous instructions then you could eliminate the "clear carry".

NOTE: if carry is set use "addlw 0xC0" instead


Regards
Sergio Masci
--=20
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