[Coco] CoCo 3 Serial Interrupt

[Brett Gordon]

I'm thinking the CoCo 2 and 3's use the serial interrupt for the "CD" line,
not the "RX" line (unfortunately), so the coco could send more data to a
serial printer.  I've often though about shorting the "CD" line and the "RX"
line together for an interrrupt driven serial receive, but appearently, the
reverse int logic would foobar this idea (although... I thought the PIA
could be configured to reverse this....)

On Fri, Oct 15, 2010 at 3:12 PM, Darren A <mechacoco at gmail.com> wrote:

> On 10/15/10, tim lindner wrote:
> > I was reading Tepolt recently and it said the serial interrupt
> > occurred then the serial line when from low to high. Is this correct?
> >
>
> ---
>
> I've never tried it, but while looking at the CoCo 3 schematic some
> time ago, I noticed that as well.
>
> The serial input signal coming out of the SALT chip goes directly to
> the PIA and is also inverted by U15 before going to the active low
> interrupt pin on the GIME.  An interrupt should therefore be triggered
> on a transition from logical 0 to 1.  Seems kind of pointless since I
> would exepct an interrupt to occur on a start bit which is a
> transition from 1 to 0.
>
> Darren
>
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-- 
Brett M. Gordon,
beretta42 at gmail.com