gnupic: Re: [gnupic] simulating an interrupt
Subject:
Re: [gnupic] simulating an interrupt
From:
Robert Pearce ####@####.####
Date:
10 Dec 2006 13:11:06 +0000
Message-Id: <R966BvCfYAfFFwWA@daniel.huneausware.local>
On Sat, 9 Dec 2006, Maxim Wexler ####@####.#### wrote :
>
> I'm not even sure what to expect. Like I say, once it's running, how do
>you "interrupt" it without stopping it? Hope that makes sense.
It should be possible, using the breadboard, to toggle one of the port B
bits. However, there are a couple of points to note:
The change of state interrupt on PORTB is actually triggered when one of
the bottom four bits differs from the last value _read_by_the_CPU_ -
your code never reads port B. You need to add:
movf portb,w
in the ISR before clearing the interrupt bit, and possibly also just
before payrol:
It shouldn't be needed, but it's good practice to explicitly set TRISB
to input.
Pins connected to nodes don't always respond to the breadboard mouse
click. If you want to be absolutely certain, you could connect a pull-up
resistor and a switch to ground. Except the current switch module is a
two-pin device, and there's no convenient ground module. So you need to
create a ground by using a pull-down resistor of zero ohms. However, an
unconnected input pin should be toggle-able with a mouse click.
--
Rob Pearce http://www.bdt-home.demon.co.uk
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