Re: Anyone ever attach a mono LCD to a PET?

From: Rob Clarke <*crock_at_clarke-family.org.uk*> Date: Wed, 9 May 2012 13:43:21 +0200 Message-ID: <3c9756f1dabe68107652c5fc306538aa.squirrel@clarke-family.org.uk> · crock_at_clarke-family.org.uk

> That LED in the F row, I also have it. Strangely enough I don't remember
> any LEDs like that from back when I first saw PETs at the school
> computer club. Maybe it isn't supposed to light up, so that may be why I
> don't remember it?

The LED was only used in the V1 ROMS and is used as a diagnostic LED. If
you have the original PET 2001 service documentation it comes with two
dongles which attach to the user port and the keyboard. The kernal checks
for the presence of the dongles and performs some basic ROM/RAM/IO test
and the LED flashes to indicate the status. It's connected to port A of
PIA1 so you can turn it on by setting $e810 to #$0b. Obviously doesn't
work from BASIC as this is also the KB scan outputs.

Rob

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