>
>> I really think the appropriate port bits can be set low once, during
>> initialization using a movwf.
> that depends on what your app is doing with the rest of the port
>
>> Then you can do bsf and bcf TRIS all you
>> want. The read/modify/write problem is only a problem when dealing with
>> a
>> PORT and is due to external loading keeping a pin from moving
>> immediately
>> after a write.
> that is one situation in which it occours yes
>
> the problem that is relavent to this discussion comes when you are using
> some outputs on a port as open collector ans some as normal outputs.
>
> lets say there is a normal output on A1 and a pin being driven as open
> collector by use of tris on A0 which is pulled high
>
> #init, all of port A as an output driving low
> CLRF PORTA
> CLRF TRISA
>
> #make A0 an input allowing it to float high
> BSF TRISA,0
>
> #make A1 high,
> #unfortunately due to RMW this also makes bit 0 of PORTA high
> BSF PORTA,1
>
> #make A0 an output again, we throught we would be making
> #it drive low but in fact we end up making it drive high
> BSF TRISA,0
>
> of course if we used LATA rather than PORTA this code would be fine but
> unfortunately only the 18 series have LAT.
>


I agree completely! Another way around this is to keep a mirror of the
PORT in RAM. Do the bsf and bcf on the mirror, then copy it to the port.

Harold

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