Re: Weird issue with the Pet 2001-N

From: Francesco Messineo <francesco.messineo_at_gmail.com>
Date: Fri, 5 Apr 2019 09:05:34 +0200
Message-ID: <CAESs-_xuvrVB=nynMxYyKjmQaYJW_Anktii0-PKyDo+NL5YdLQ_at_mail.gmail.com>
On Fri, Apr 5, 2019 at 8:29 AM David Roberts <daver21145_at_gmail.com> wrote:
>
> 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.

if this would be the fault, then every byte entered on screen would
suffer the same problem, so it would result in a lot of syntax errors.
If only the variable names are affected, I would still think about a
fault in bank 1 DRAM/data bus.

>
> 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 21:17:38

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