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'[PIC]: Sleep again, will HI to LO pulse ONLY, exit'
2002\03\26@175924 by Gary

picon face
Hi,

I need the exact sequence of events on a PIC!

I put PIC to sleep, set to change on RB0 pin High to Low transition.



Now does a High to Low transition only, (I.E. not High to Low transition and then back to High) awake the PIC?

As in my experiments it is only the HLH sequence that wakes it?

Is there any way of it working on just HL pulse, or is that just the way the PIC is designed to work?

Thanks Gary

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2002\03\26@181327 by David Duffy

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Gary wrote:
>I need the exact sequence of events on a PIC!
>
>I put PIC to sleep, set to change on RB0 pin High to Low transition.
>
>Now does a High to Low transition only, (I.E. not High to Low transition
>and then back to High)
>awake the PIC?
>
>As in my experiments it is only the HLH sequence that wakes it?
>
>Is there any way of it working on just HL pulse, or is that just the way
>the PIC is designed to work?

You can change the trigger edge of RB0 in the option register. (bit 6)
Taken from the Microchip datasheet:

INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of RB0/INT pin
0 = Interrupt on falling edge of RB0/INT pin

Regards...

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2002\03\26@192732 by michael brown

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>Hi,

>I need the exact sequence of events on a PIC!

>I put PIC to sleep, set to change on RB0 pin High to Low transition.

>Now does a High to Low transition only, (I.E. not High to Low transition
and then back to >High) awake the PIC?

>As in my experiments it is only the HLH sequence that wakes it?

>Is there any way of it working on just HL pulse, or is that just the way
the PIC is >designed to work?

No, that is not how the PIC's RB0/INT interrupt works.  I works exactly the
way you would expect it to (surprisingly enough).  I'm assuming that
H=5volts and L=gnd.  If the signal line is primarily H all the time AND you
want it to trigger on button down (where the button connects the pin to
ground when pushed), you will want to set the PIC to trigger on a "falling"
edge.  The PIC will trigger the interrupt precisely when the button is
pressed down.  If you want it to occur on button release (you will want to
trigger on a "rising" edge.  Of course, without debouncing your button, your
interrupt routine is likely to run dozens of times on one button press
(especially if it is a short routine).  :-O

Newbie PIC Tip of the Day:  Make sure you have the watchdog timer disabled

2nd Tip:  Take your e-mail address out of the "Reply-to:" setting so that we
don't have to change the address to the piclist's.

Hope this helps.

michael brown

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