[sdiy] Prophet 5 Rev3 RAM issues

[Gordonjcp]

On Sun, Sep 20, 2015 at 10:47:06PM +0100, John Henson wrote:
> I have been looking at the schematics for all of the Rev 3 CPU
> sections, and the 3.3 did indeed have a 6116 in it, unfortunately
> the firmware was rewritten each time for the new revisions, and a
> completely different NVRAM access scheme was used for the 3.1
> compared to the 3.0. The 3.1 also ditched the 2708 EPROMS at last,
> but even after all the mods necessary and yet another daughter board
> built, I don't have the 9.1 firmware images (or any 2716's either).
> Unfortunately both these Prophets came in because the owners thought
> that the battery needed changing and they are not prepared for, or
> willing to pay what it may take to put these right.
> 

I don't have a copy of the service manual to check, but is firmware actually likely to be an issue?  As in, are the /CS, /OE and /WE pins driven by IO pins or by the normal CPU pins and address decoder?

-- 
Gordonjcp MM0YEQ