Re: Weird issue with the Pet 2001-N

From: David Roberts <daver21145_at_gmail.com>
Date: Fri, 5 Apr 2019 07:28:24 +0100
Message-ID: <CAC5emFE-jBf9vEOaj_t9Md-Ny=S-119ZbPUHdX6Qjiu3ss03Vg_at_mail.gmail.com>
It could also be the octal read buffer from the screen RAM dropping a bit
rather than the main RAM itself. The 'Y' gets entered onto the screen
correctly. I can't just remember off hand whether the command line is
constructed in main RAM or read from the screen RAM when RETURN is entered.

Just a thought, I will have a look in more detail later on today.

Dave

On Wed, 3 Apr 2019 at 08:19, Francesco Messineo <
francesco.messineo_at_gmail.com> wrote:

> On Wed, Apr 3, 2019 at 3:57 AM Steve Gray <sjgray_at_rogers.com> wrote:
> >
> > Sounds like bit 3 is being dropped when stored as a variable. That would
> suggest that you have a bad ram at the top end of user memory space.
>
> That could be possible, but the fault must still allow the RAM
> initialization and check to function properly, it the correct bytes
> free amount is printed at startup.
> RAM is initialized with $AA if I remember correctly, so bit 3 = 0
> would be possible and not detected.
> If it's a 2001N with two banks, the problem is likely on bank1
>
> Frank
> >
> > Steve
> >
> >
> > > On Apr 2, 2019, at 9:07 PM, David Laffineuse <davidlaffineuse_at_me.com>
> wrote:
> > >
> > > The keyboard seems to be working perfectly fine.
> > > For instance if I type on the key 'Y', the letter Y is displayed on
> the screen.  However if I set a variable to Y, e.g. a$="Y" then I print a$,
> I get a Q on the screen...
> > > The same occurs with I which produces an A, H which produces _at_, Z
> which produces R, X which produces P, 8 that produces 0, and 9 that
> produces 1.  All the other letters are fine.
> > > What is going on?
> > > David
> >
> >
>
>
Received on 2020-05-29 21:17:54

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