Re: TDS784C


Ragnar S
 

Hi all,

There is some calibration data in the EEPROMs on the acquisition board, but also in the NVRAMs on the CPU board.

I have been told that you should never swap acquisition boards between scopes without also moving the NVRAM contents.
Also, there are indications that there is calibration data that not even the field service calibration data will update, that was written at the factory.

You are right that the NVRAMs are also used for storing waveforms, settings and other stuff.

If you care about your scope I would _absolutely_ recommend backing up your NVRAMs and your EEPROMs.

There are some DOS programs build for National Instruments GPIB drivers, mainly tekfwtool and getcaldata, as well as the floppy based tools that John pointed out, tdsNvramFloppyTool, that also has a Java program that can verify the checksums of your dumps.

Both ways of getting your EEPROMs and the NVRAMs are a bit fragile, so I would recommend using two separate methods, or at least do it twice, and check that there is no difference between the results.
Sadly there always is a difference in the first bytes of the NVRAM dumps, because that is where there real time clock is mapped (in the DS1486).

Since I had no National Instruments GPIB interface around (but an Agilent USB one), and no DOS machine (but linux and unix machines), I did the little work it took to make them compile clean on Linux, on a Raspberry Pi in my case, fixed some simple makefiles and made a collection of the tools. Another guy wanted to run them on a Mac, which was trivial to fix as well, so I added that too.

You can find my collection here:
https://github.com/ragges/tektools

Best regards,

Ragnar

On 28 Jan 2020, at 18:23, Stephen Hanselman <kc4sw.io@...> wrote:

Speaking only from experience with TDS 540x, yes the calibration is kept on the acquisition PCA. I think, but have not taken the time to prove, that the primary use of the NVRAM is to store trace data. Everyone of the NVRAMs I have read seem to have a pile of "empty" space in them along with a bit of stuff relating to options, date, time, and the like.

Just as easily though I could be FoS.

Steve

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Siggi
Sent: Tuesday, January 28, 2020 7:05 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] TDS784C

On Tue, Jan 28, 2020 at 8:39 AM JJ <jajustin@...> wrote:

You need to be concerned with the NVRAM chips - DS1486 clock chip and
the DS1650/DS1250. They have internal batteries that hold the
calibration constants and options info.
It's my understanding that the calibration constants are stored in EEPROM on the acquisition board. There's no reason to worry about the options, as it's easy enough to restore those with GPIB or other means.





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