[Coco] CoCo 3 Serial Interrupt

Darren A mechacoco at gmail.com
Fri Oct 15 15:12:26 EDT 2010

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.


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