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'[PIC]: One PIC triggering another'
2001\10\02@172654 by andyf

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I have an application where I need a couple of PIC's to trigger another.

Can I just run the output of a PIC to the input of another, hold the output low and then put it high when I want the 'receiver' to be triggered?  The 'receiver' would be looking for a high.

If I want either of two PIC's to trigger a 'receiver', can I just run the outputs through a couple of diodes (maybe 1N914's) and then common the cathodes together on the input of the 'receiver'?  That way, if either of the outputs go high, they will trigger the input of the 'receiver'.

Am I way off base here?  Any ideas would be appreciated.

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2001\10\02@180918 by Byron A Jeff

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On Tue, Oct 02, 2001 at 02:12:54PM -0700, Andy Fenstad wrote:
> I have an application where I need a couple of PIC's to trigger another.
>
> Can I just run the output of a PIC to the input of another, hold the output low and then put it high when I want the 'receiver' to be triggered?  The 'receiver' would be looking for a high.
>

As long as the chips are on the same board it will be fine. I would caution
to either have handshaking, where the receiver indicates on another line that
it received the trigger, or if possible to use an onboard peripheral that
can interrupt, such as the INT pin. You want to guarantee that you don't
miss any triggers.

> If I want either of two PIC's to trigger a 'receiver', can I just run the outputs through a couple of diodes (maybe 1N914's) and then common the cathodes together on the input of the 'receiver'?  That way, if either of the outputs go high, they will trigger the input of the 'receiver'.
>

You can do that in software too. Configure your output as a 0. Instead of
changing the output pin from 0 to 1, change the pin from output to input.
When it's an output, it'll be 0. If it's an input, it'll be Z. Add a pullup
and you can connect as many triggers as you like. No diodes required.

> Am I way off base here?  Any ideas would be appreciated.

As long as it's within a single board, you should be fine. Once you need to
get offbaord, you may want to look at some driver or another.

BAJ

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