Re: A parallel interface for PET, VIC-20 and C64/C128

From: William Levak (wlevak_at_cyberspace.org)
Date: 1999-08-04 05:05:22

On Tue, 3 Aug 1999, Andre Fachat wrote:

> Marko Mäkelä wrote:
> > The only unanswered question is: What is the DIAG pin on the PET user port
> > used for?  Can I safely program it as a '1' output and use it as a voltage
> > source for the 74HCT74 chip?
> 
> If you pull it low (I think) the Kernal does not init BASIC and
> directly enters the monitor on startup.
> 
This is true for all but the original PET.  The original PET does not have
the monitor.  It has a built-in diagnostic routine which runs instead.

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