TDS 684C NVRam Backup

[Armadillo]

Dear fellow members;

After reading some of the episodes of NVram problems and the desoldering difficulties, I decided to backup a copy of my TDS 684C Dallas NVRam for  safekeeping purpose.

The NVram Chip used in the TDS 684C is a DS1250Y which is 512K X 8 non-volatile static rams. This is in contrast to the DS1650Y chip as used in the TDS520 scope of same memory size and same pin counts.

However,  I can only find memory map details for the TDS520 scope. The NVram base address is at 0400 0000–040F FFFF. But I am unable to find the NVram memory map details for the TDS 684C scope.

Has anyone backup the nvram data from the TDS 684C before? Any info would be appreciated. Thanks.

I assumed the memory to be same as the TDS 520 and downloaded the 'nvram' data from my scope, which looks something like attached. However, I have no idea if the data is any correct. Any ideas? thanks.

[james_s]

IMHO the easiest and most reliable thing to do is desolder the chip and dump it with an EPROM burner. Obviously this is a good time to install a socket so you can easily change it later. AFAIK there's nothing critical in the DS1250, it's used for saving waveforms and user settings. The timekeeper holds the options and error log, it can be backed up in a similar manner. Cal data is held in eeprom on the acquisition board.

[Armadillo]

Thanks james_s, that is really a important piece of information there.

[Armadillo]

I am inclined to think that the GPIB read of the DS1250Y of the TDS 684C was OK. Attached interesting pattern comparison of feedback.loop TDS540 DS1650Y with my TDS 684C. You can see the peculiar "white 00" pattern similarity between the 2, though some of the bytes are not the same. Particularly not the same is the error logs starting page, but I don't expect the 2 to be the same anyway. When I find time, I will desolder the chip and read it with my GQ-4X to ascertain once and for all that the GPIB read can be reliable. I hope you can visualize the pattern attached.

Left [TDS 684 from Armadillo] ===========================================Right [TDS 540 from feedback.loop]

[nctnico]

Do a memory clear (this may be called secure erase or something like that). Most of the data stored in the NVRAM is reference waveforms. If you do a memory clear this data will be zeroed.
If you desolder the NVRAM then solder it into a socket with turned pins and put a socket with turned pins in the scope's CPU board. Soldering the NVRAM into a socket is essential because the tin on the pins will cause poor contact in both the EPROM reader and socket. I've done this a couple of times in various scopes but it seems I never took a picture.

[chihaxinh]

Hi All

Anyone have NVRAM data TDS520B  could share me ? I dump data but see allmost blank (FF) 

[Armadillo]

Do a memory clear (this may be called secure erase or something like that). Most of the data stored in the NVRAM is reference waveforms. If you do a memory clear this data will be zeroed.
If you desolder the NVRAM then solder it into a socket with turned pins and put a socket with turned pins in the scope's CPU board. Soldering the NVRAM into a socket is essential because the tin on the pins will cause poor contact in both the EPROM reader and socket. I've done this a couple of times in various scopes but it seems I never took a picture.

OMG, there are just reference waveforms.!

Thanks for the information. Regarding turned pins socket, I am afraid they are rather rigid and the outline dimension don't seems to align well with the existing holes. Furthermore like you say the need to solder-in socket, in good practice principles, I am really not in favour of adding extra capacitance to the already slowed speed of the chips by installing IC sockets.
However, for the ease of swopping the chips in future, saving another desoldering and risks lifting the pads, I am considering to use the cheaper flat pins socket instead because the legs are more flexible and will align well with the holes. In your opinion, are there any areas of concern here? thanks.

[Armadillo]

Finally found time to unsolder the NVram and the time-keeper chips;

So the comparison between GPIB read and the GQ4X read and the findings are as follows;

Findings;

1.0 The TDS684C NVram memory address is the same as the TDS520 map
2.0 From 0000 to 1FFFF [131,072 bytes], the content differs between the 2 methods [could be waveform storage space]
3.0 From 20000 - 7FFFF [393,216 bytes[, the contents are completely the same
4.0 The time keeper DS1486 bytes at 33 to 3A [8 bytes] will change between read indicating that the real time clock is still alive. [time register bytes]

Verdict;

IMHO: The GPIB read of the NVram is reliable. I would recommend this method to backup the NVram before any soldering works as the batteries of the NVrams may be so weak that it cannot withstand the stray current of the soldering iron tip. This concern is was also raised in the TEK forum.

Luckily the scope still works and the old Dallas Chips still last a lifetime! [touch wood]

 

[Armadillo]

Part 2

[Armadillo]

Part 3..

[Jwalling]

FWIW, I have a DS1486 that went bad in a TDS700 scope (Read/write data failures on addresses from 0 to 3F) but the batteries (there are two inside the chip!) are still OK. The one closest to pin 1 measures 3.01VDC, the one closest to Pin 16 measures 3.13VDC.
The date code of the chip is the 30th week of 1998. I'm beginning to think these will easily make 30 years or more before they crap out.

[Armadillo]

I'm beginning to think these will easily make 30 years or more before they crap out.

That opens up another area of thoughts. Basing on this formulation, in another couple of years, these oscilloscopes are going to crap without the replacement chip. We know that ebay chip is fake crapped, maybe worse than year 1998. What are we going to do about it?

Any positive ideas how we can prolong the life of these scopes without everyone scrambling for the chip?

[Bushougoma]

IMHO: The GPIB read of the NVram is reliable. I would recommend this method to backup the NVram before any soldering works as the batteries of the NVrams may be so weak that it cannot withstand the stray current of the soldering iron tip. This concern is was also raised in the TEK forum.

Don't trust ANY dump from any Dallas SRAM on a GQ-4X it is very likely your programmer is the issue.

I had an issue where mine wouldn't read a DS-1220Y the dump was just repetitive hex. Reading a parallel SRAM is as simple as it gets and apparently they couldn't even get that right.

So I put it into my TL866 and it read and programmed the replacement properly.

Not wanting to let this go I sent the chip to the programmer manufacturer to investigate and they sent me a new version of the programmer software that did read the chip properly. So to test it I went to program a new Dallas chip I had (same part number) and it again didn't write or read properly I could read and write to the old chip though .

It can't even program 27C series EPROMs properly out of the box. If you do use it for EPROM programming click the "i" button to verify that all of the voltages are correct because the majority of the time they are not.

For example by default it sets the WVCC (Write VCC) on most EPROMs to 5.5 volts when most datasheets clearly state to raise the VCC to 6.25 volts when programming.

Another example many EPROMs have their read VPP "not set or invalid" by default don't know if that means the VPP pin is connected to ground or the pin is floating... never checked it should be connected to VCC when reading of course. This all can be modified in the devices.txt file which is where I spend most of my time getting it to work properly instead of actually using the programmer .

When I do have to use it which isn't that often thank goodness (when dealing with older 21 volt VPP EPROMs for example) I expect to have to tweak something to get it to work.

</RANT>

[ArcticGeek]

I would agree with the problems mentioned with the GQ-4X programmer.  I have had all kinds of issues programming and reading various parts on the GQ-4X programmer, so much so that I refuse to use it any more.  My most recent experience was with an AMD 29LV160 flash part - when reading the part I get different data depending on whether the speed was set to 0, +1, or +2.  The TL866 programmer read it fine every time.  I've also had numerous problems reading Dallas NVRAMs that are used in the Tek TDS600/700 scopes.

The contents of the DS1250 are not critical, as others have mentioned it only stores saved waveforms and saved user settings.  In fact, the scope will boot just fine if you completely remove the DS1250.  The original DS1650 that was used in these scopes is long obsolete, but the DS1250 works fine as a substitute. I've replaced dozens of these parts in various TDS600/700 series scopes.

The DS1486 is much more important - it actually holds the scope options as well as the date & time.  These parts went obsolete in the 2010 time frame as I recall.  You can buy these parts on Ebay, but they are fake.  I know this because some of these parts will have a datecode of 2014 or newer!  I've also verified that the some of the mechanical dimensions of these fake parts are also out of spec, another indication that they are not authentic.  For example, the pin length on the fake China parts are longer than what the Maxim spec indicates.  These parts might work okay, but I question for how long.  I do plan to start a new thread on an analysis of some of these fake parts, but just haven't had the time yet.

[james_s]

I'd be curious to know more about the fakes. I got a DS1250 from ebay because the one in my scope has a bulge in it and it turned out to be a re-mark with clear evidence of the top being sanded and a bigger giveaway is that it arrived with data on it. It may be a genuine chip that was simply relabeled so it may be usable if I mill out the battery and replace it. I got a refund so one can get these fake/relabeled chips for free. I think the MO of many of the sellers is to just refund anyone who complains and bank on the fact that most people won't notice or won't bother. I'm really tempted to buy samples from a bunch of different sellers and xray them along with a real one.

It would be easy to make a DS1250 clone using a SRAM and battery backup management IC but I'm not sure about the ones that include a RTC. I wish the Chinese companies would just offer a compatible IC under their own brand rather than a counterfeit Dallas chip, the Dallas parts are so expensive that they could easily make a quality replacement that is not a fake.

[Armadillo]

Would someone provides the precise micro surgery template reference to left edge and Top Level of the IC, on how to expose the battery terminals for external connection. Photo of this precision surgery operation would be greatly appreciated. So instead of cutting, we can just precisely mill/drill 2 small holes for insertion connection.

I have just paid for a knowingly fake IC from ebay ready to perform this micro surgery operation in anticipation for the future and coming TDS apocalypse.

In probably 5 years time, the ebay will be flooded with TDS oscilloscopes, I imagine.

[james_s]

I'm going to try to xray a batch of stuff over the weekend if I can find the time, in which case this is one of the items on my list. I've done quite a bit of de-potting epoxy potted bricks but something small and delicate like these are a lot easier if you can see what's inside ahead of time.

[Bushougoma]

Would someone provides the precise micro surgery template reference to left edge and Top Level of the IC, on how to expose the battery terminals for external connection. Photo of this precision surgery operation would be greatly appreciated. So instead of cutting, we can just precisely mill/drill 2 small holes for insertion connection.

Just look at the epoxy under a bright light and you usually can see the outline of the cell. At least that was the case with the old Dallas SRAMs I have don't know about the RTCs.

[james_s]

I xrayed a DS1250 last night, still need to scan the films and then I can post the images. The battery is on the end under the Dallas logo laying flat above the board. It sits very close to the top surface, there is maybe 1mm of epoxy over it. Below the battery is a PCB with what looks like a standard surface mount SRAM and below the battery is what I assume is the power management IC.

[Armadillo]

I xrayed a DS1250 last night, still need to scan the films and then I can post the images. The battery is on the end under the Dallas logo laying flat above the board. It sits very close to the top surface, there is maybe 1mm of epoxy over it. Below the battery is a PCB with what looks like a standard surface mount SRAM and below the battery is what I assume is the power management IC.

Thanks James_s, that is a very complete electronic lab you have there.

Is the dS1486 same construction as the ds1250?

The x-ray is really something new. Maybe a descriptive introduction to us?

I only knew Mikeelectricstuff, Applied Science Ben, and now James-s have the machine. who else?

[Armadillo]

I would agree with the problems mentioned with the GQ-4X programmer.  I have had all kinds of issues programming and reading various parts on the GQ-4X programmer, so much so that I refuse to use it any more.  My most recent experience was with an AMD 29LV160 flash part - when reading the part I get different data depending on whether the speed was set to 0, +1, or +2.  The TL866 programmer read it fine every time.  I've also had numerous problems reading Dallas NVRAMs that are used in the Tek TDS600/700 scopes.

The contents of the DS1250 are not critical, as others have mentioned it only stores saved waveforms and saved user settings.  In fact, the scope will boot just fine if you completely remove the DS1250.  The original DS1650 that was used in these scopes is long obsolete, but the DS1250 works fine as a substitute. I've replaced dozens of these parts in various TDS600/700 series scopes.

The DS1486 is much more important - it actually holds the scope options as well as the date & time.  These parts went obsolete in the 2010 time frame as I recall.  You can buy these parts on Ebay, but they are fake.  I know this because some of these parts will have a datecode of 2014 or newer!  I've also verified that the some of the mechanical dimensions of these fake parts are also out of spec, another indication that they are not authentic.  For example, the pin length on the fake China parts are longer than what the Maxim spec indicates.  These parts might work okay, but I question for how long.  I do plan to start a new thread on an analysis of some of these fake parts, but just haven't had the time yet.

You guys are right on, the GQ-4X is a piece of crap, just shit out on me and hanged the software.   
Not going to waste my time on it.

[Bushougoma]

You guys are right on, the GQ-4X is a piece of crap, just shit out on me and hanged the software.   
Not going to waste my time on it.

I hated when I had to come to terms with that fact especially since the base model cost me more than double what the TL866 did. Guess you get what you pay for doesn't always apply.

[james_s]

Thanks James_s, that is a very complete electronic lab you have there.

Is the dS1486 same construction as the ds1250?

The x-ray is really something new. Maybe a descriptive introduction to us?

I only knew Mikeelectricstuff, Applied Science Ben, and now James-s have the machine. who else?

I don't have the machine in my lab, it would be very convenient but it's a rather large piece of equipment and I don't think the powers that be would appreciate me operating such a thing in a residence. I have pretty much full access to it after hours though and can xray various non-living stuff as long as I provide the film.

I can't say about the DS1486 without looking but I suspect it to be the same. If anyone has a dead one to send me I can find out.

[Armadillo]

Thanks James_s, that is a very complete electronic lab you have there.

Is the dS1486 same construction as the ds1250?

The x-ray is really something new. Maybe a descriptive introduction to us?

I only knew Mikeelectricstuff, Applied Science Ben, and now James-s have the machine. who else?

I don't have the machine in my lab, it would be very convenient but it's a rather large piece of equipment and I don't think the powers that be would appreciate me operating such a thing in a residence. I have pretty much full access to it after hours though and can xray various non-living stuff as long as I provide the film.

I can't say about the DS1486 without looking but I suspect it to be the same. If anyone has a dead one to send me I can find out.

Yeap!, it would be extraordinary to include a X-Ray machine in an electronic lab. Cause even the signal path Shahriar with his close to $million dollars equipment don't have one, not even a wire bonding machine.  I think the room need to be lined with lead to comply with country code. Ben is that scientist class, exception.
 

[KE5FX]

Yeap!, it would be extraordinary to include a X-Ray machine in an electronic lab. Cause even the signal path Shahriar with his close to $million dollars equipment don't have one, not even a wire bonding machine.  I think the room need to be lined with lead to comply with country code. Ben is that scientist class, exception.

Y'all need to check out Aurora's thread.  It hooked me.  Low-energy cabinet machines are perfectly safe and not all that expensive.  The trick is finding one that's being sold with its digital imaging hardware.