When the stack and the variables are kept in volatile ram held up by a
battery and that battery gets old the computer runs wild. I doubt
there's any code stored in the ram unless its self modifying which might
be needed in the 8051 architecture. Its important that at this age of
the Omni VI that the lithium cell on the control board be good. If its
not all kinds of odd things can happen. If its under 3 volts when the
radio is not powered its overdue for replacement. The radio has a good
chance of working better if its reset at power up, the master reset that
cleans all the memories. And it will need that after a battery replacement.
The code would be in the 27C256 EPROM and that code has to include
setting up any code in the RAM if there is anything but system variables
and the code stack there. That has to be in the EPROM part of the code
to enable working to start after a master reset.
The battery is in a holder, might be a 2032 but I can't see numbers on
this official scan.
The RAM chip is not as easily found in DIP as in SOIC, but Jameco has
them in quantity for less than $3 each, but it won't hold up content if
the battery is going dead.
73, Jerry, K0CQ
On 1/14/2011 6:38 PM, Neal Laugman wrote:
> I do see that Maxim does offer a drop-in replacement for the DS1285.
> I'm curious enough about this as to contact TT next week.
>
>> Optimized assembler certainly is
>> different for each chip. My experience is that it can take a man year
>> to become half way competent in assembler for a particular chip, to
>> know whether it was a good choice or not. When I first did that the
>> choices were about 5, now there are thousands to choose from. Yet
>> some still have the same op codes as those five I had to choose from
>> in 1975 but can address much more memory and run much faster.
>
> I was a few years behind you and yes - it takes quite a while to pump
> out good assembler. The redeeming thing here is that it's just
> basically control functions and and not fast fourier transforms! 8051
> tech is alive an well along with it's codebase (who would have guessed
> this back in the late '70s).
>
>> I also see a lithium cell on the board.
>> Has anyone ever replaced that cell when there was a control board
>> problem? Every other radio that vintage with a lithium cell has
>> needed replacement. That might be worth the bother in the Omni VI and
>> VI+.
>
> I know from experience that an IC-751 can totally loose it's firmware
> if the lithium cell dies, but I'm thinking it's more than just losing
> code. You suggested a disassembler (if that would solve the problem)
> but it's kind of an "in your face" thing to do to a company you like
> and what to maintain relations with. But, on the other hand, if someone
> would just "happen" to acquire the code through disassembly or by some
> other means, the problem could be solved to everyones satisfactions -
> if in fact it is code-related.
>
> Since there is a lack of information, I'll give it a rest until I can
> ascertain more facts next week and then continue from that point. Maybe
> someone at TT will be in a sharing mood by then.
>
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