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'Does a write to PORTB cause an INT?'
1998\03\26@013432 by bossmonkey

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Greetings:

I'm using a 16C84.  I am using pins 1-7 as output and pin 0 as input, for
the INT interrupt.

My question:    If I write to PORTB as a whole, will I cause an INT
interrupt?

My guess:  No, INT samples the pin, not the latch.  The write will write to
the latch only, and pins set as input (RB0, aka INT) will not be affected.

The other question:    Aren't the interrupt flags set even when GIE is
cleared?  Will an interrupt occur when GIE is then set?

My guess:    I can't reason this one out from the databook.  I think that
when GIE is set that any  interrupts with their enable and flag bits will
cause an interrupt to occur

Right?  Thanks for any help.
Regards,
Mick Reed - electrical engineering student -
spam_OUTmichael.reedTakeThisOuTspambbs.chemek.cc.or.us

1998\03\26@015125 by Andrew Warren

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bossmonkey <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU> wrote:

> If I write to PORTB as a whole, will I cause an INT interrupt?
>
> My guess:  No, INT samples the pin, not the latch.  The write will
> write to the latch only, and pins set as input (RB0, aka INT) will
> not be affected.

   Mick:

   Your guess is correct; writing to the port will not generate an
   INT interrupt.

> Aren't the interrupt flags set even when GIE is cleared?  Will an
> interrupt occur when GIE is then set?
>
> My guess:  I can't reason this one out from the databook.  I think
> that when GIE is set that any  interrupts with their enable and
> flag bits will cause an interrupt to occur
>
> Right?

   Right again.

   -Andy

=== Andrew Warren - fastfwdspamKILLspamix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499

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