Re: 2440 nvram (was: NVRAM back-up battery change on a 2715..... avoiding disasters)


Szabolcs Szigeti
 

Hi,

No, there is no other writable store in the instrument what i know about,
and there doesn't seem to be any on the schematics. I think what the SM
says here is when you press the button, it recalculates some values and
writes it to the nvram. But this needs to be done after every change in
setting the pots. So for the original question of is there a real need to
save the 2440 nvram when _it is in cal_ but the nvram needs to be changed,
the answer is no, as the scope can be brought back to calibrated state by
running the self cal and ext cal. This does not need any physical setting
inside the scope (well except for the cal enable jumper). If the scope is
out of spec (which an old one most likely will be), then the answer is no
again, because you have to do the full adjustment procedure anyway.
However, I'm no authority on this, I did do calibration on a number of
2440s and experimented with them too, but I don't know how the firmware
actually works. Would be interesting to reverse engineer though, as there
are a number of really cryptic features in the calibration menus, about
which the Sm doesn't say a word.

Szabolcs


Raymond Domp Frank <hewpatek@gmail.com> ezt írta (időpont: 2019. nov. 8.,
P, 17:30):

On Fri, Nov 8, 2019 at 02:45 PM, Szabolcs Szigeti wrote:


But these are all adjustments requiring turning trimmer pots.
I had a quick look in the SM. The Adjustments chapter (5) mentions e.g. on
pages 5-8 and 5-10 (in my manual) "WRITE TO CAL STORE" and on page 5-13
"Pushing A HORIZONTAL MODE causes the instrument to make firmware
corrections...".
I assumed that those writes and corrections were to the NVRAM. If you're
right, the 2440 has yet another kind of "writable ROM" than the NVRAM. Do
you know if that's true and if so, what kind of storage it is?

Raymond



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