> >Now that gets me to thinking: Here is  a neat trick to get a 'push-pull'
> >output from two PORT A pins:
> >
> >1: define them as analog (ADCON1)
> >2: TRIS them as outputs.
> >
> >Now, when you BSF either of them the other will automatically be cleared.
> >
> >This would have been useful in a system I built that drove a piezo
> >transducer directly off two PIC pins.
> >
>
> Guess you could always write xxxx'xx01 and xxxx'xx10, on regular
> digital pins.

Sure: But here I only have to write 1 pin and the other 'magically' switches
state. Saves me at least one instruction. Gotta have some use :-)

>  And actually, you can drive a piezo quite well using
> a single pin on a PIC. In fact, as it is, you normally have to use
> a 100-1000 ohm attenuation R in series, or it will drive you right
> out of the room.

Out of the room was the whole idea.

Actually, I used this trick to get two volume levels: for key-click prompts
and warning tones I held one output fixed and toggled the other. For the
alarm output I toggled the two outputs 180 degrees out of phase with each
other.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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