Re: option ROM into a 3032

From: Francesco Messineo <>
Date: Wed, 27 Sep 2017 22:24:38 +0200
Message-ID: <>
On Wed, Sep 27, 2017 at 8:41 PM, Ethan Dicks <> wrote:
> On Wed, Sep 27, 2017 at 12:13 PM, Francesco Messineo
> <> wrote:

>> well, the changes are really small, actually part of the same
>> character changes (modifying the
>> character itself), not the character.
> Ah... the pixels in a character cell are changing?  That's really odd.
> The path is the timing circuit reads the pair of 2114 RAMs that are
> gated over to the CHARGEN ROM then the ROM's data outputs are hooked
> to a shift register for the specific dot that's then sent up the
> 6-wire cable (video, h sync, v-sync and 3 grounds).

looks like UF6 is bad, it doesn't output the VRAM Write signal (TV RAM R/W), its
inputs are correct, so I'm going to replace it.
It might be bad on other signals too.

> If you have a petester ROM installed, then BASIC and the KERNEL ROMs
> aren't a factor, but address and data buffers could be, or address
> select logic.

yes, I'm using petester since it cycles writing and reading to VRAM so
it's easier to probe
Let's see what happens when I replace UF6.

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Received on 2017-09-27 21:00:02

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