Good morning/day Jinx.

After you put byte into port you are making bsf manipulation.
In reality PIC _is_ reading port value than modify the bit than
writes it back to port. In your example modified data is stored
exactly in port itself.

What I was saying that depending from load situation or delays
because of capacitance if you write "0"/"1" you probably won't
get it back two cycles later for say on 20MHz clocking.

I stepped onto this trouble couple times in the past. After that
if I doubt a little bit I better use shadow register technique.
All manipulations are performed under some memory cells than that
value is copied to requied port.


WBR Dmitry.

PS. Nobody beat anybody, especially by the cycle ;)



Jinx wrote:
>
> > Actually you should be very carefull using bsf operation
> > under port which is direct driving bunch of LED's. Read-
> > modify-write is a hint. As well as shadow port register
>
> Yes, I know what you mean, but there's no modification
> is there ? The bits being read are in DATAIN, not the
> port (which is only being written to), so it should be OK
>
> As they're only LEDs it shouldn't matter, but I wouldn't
> use this method with port pins that are clock lines for
> example, might be unpredictable
>
> I think you still have me beat by a cycle

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