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2465/7B NVRAM images
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Chuck Harris
NVRAM images follow the same theme, but they are not
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necessarily identical from revision to revision, or from option to option... or even day to day. Remember, the NVRAM is also the working memory for the scope, so it has all of the stack, heap and data space stored in it. Everything, but the important stuff gets erased and refreshed when the power cycles. Nothing is pre-stored in the NVRAM. A virgin NVRAM is set up from scratch by the EPROM code in the scope, and the EPROM code in the options. I have seen some funny behavior when a NVRAM (or an A5 card) from a scope is transplanted into a scope that has different options. A full calibration should be done whenever that occurs. -Chuck Harris Jean-Paul wrote: Hello all curious about NVRAMs data. |
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For what it's worth, I added a GPIB card to my 2445A without issue. It was automatically recognized and setup with the defaults. (Naturally, it doesn't have any calibrated measurements, I'd imagine the CTT or DMM option would need that before the values are particularly meaningful.)
At least with the older EAROM scopes which had limited write cycles, I doubt the nvram was used for stacks and temporary data; saner just to put in a few kb of volatile ram instead. |
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Chuck Harris
The older 2465 and 2445 have an EAROM, which most assuredly
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is *n0t* an NVRAM. writing to one takes a very specially sequenced and tested set of writes... reading is tricky too. ... and it is 14bits wide, under an 8 bit processor's use. Those scopes had separate CMOS RAM for all processor volatile use. The 2465A, and B and their brethren, all have some form of battery backed up RAM for *all* of their RAM use. The early instruments used a separate lithium cell, low power CMOS RAM, and a management circuit of tektronix's design. The later "B" instruments use a Dallas NVRAM module. If you add in an option board, its EPROM will setup the space it needs in NVRAM to default values. If you later remove the board, the A5 controller will, as I recall, complain about it. It isn't something I do very often, but I did have a bunch of A5 boards to fix, update, etc. a while back, and I recall the problems. One was fully optioned, but my test bed scope was without option. It did not like the A5 board, from a fully optioned scope, being installed in it. -Chuck Harris uniacke1 via Groups.Io wrote: For what it's worth, I added a GPIB card to my 2445A without issue. It was automatically recognized and setup with the defaults. (Naturally, it doesn't have any calibrated measurements, I'd imagine the CTT or DMM option would need that before the values are particularly meaningful.) |
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I have no experience with GPIB. My 2465BDM has GPIB.
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School is about to start. While I will be consumed with school, I would like have the procedure to backup my EAROM AND NVRAM on the 2465BDM on a file that I might try to do it when time allows. I use a MAC. I will be putting a Window 10 partition on one of my computers soon. Macs have no parallel port. I do have USB and LAN ports. I understand I¡¯ll need some kind go USB or LAN to GPIB converter. So, does anyone have a suggestion for said converter? Would someone be so gracious as to outline what I need to do to look at my GPIB once I get the converter. Lastly, could someone tell me how to get into the various RAM on the 2465BDM. Thank you all, larry On Sep 1, 2019, at 10:06 AM, uniacke1 via Groups.Io <uniacke1@...> wrote: |
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I have used several GPIB adapters; the USB ones seem to be the most popular. I found them hard to use and very fussy about what hardware and operating system they're installed on. For all those reasons, I developed KISS-488. I have not tried saving or restoring NVRAM via KISS-488, but I'm quite sure it can be done and I'd be happy to work thru it with you for the sake of education for both of us. Can you get me a scan or PDF of the section of the manual that covers those operations for your unit?
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I had a run on KISS-488 based on a youtube video at ( ) so I've been out of stock since the day after that came out. I have everything for the next run except the assembled PCBs, and those are due in this week. I'll be listing it again on eBay as well as announcing on this list when I have KISS-488 to ship. Steve Hendrix At 2019-09-01 11:45 AM, Lawrance A. Schneider wrote:
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Chuck Harris
Your 2465"B"DM does not have an EAROM. The EAROM was exclusive
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to the first model of the series: 2465. The "A", and "B" models all have some form of battery backed up CMOS memory. The "B" models above serial number 50,000 have NVRAM modules made by Dallas Semiconductor. There is no point in backing up these memories. By the time they go bad, you have most likely needed a calibration for more than 15 years. I am pretty sure that GPIB will not help you back up anything related to the calibration constants. Tek wouldn't have wanted you to do that, as calibration is called for on a yearly basis. The GPIB is there to help you quickly, and reliably, setup the front panel to run a specific test. This is very important to folks that use the 2465 family scopes in a factory environment. The military used it extensively to work with test sets used for calibration, repair, and setup of avionics and other sophisticated military hardware. -Chuck Harris Lawrance A. Schneider wrote: I have no experience with GPIB. My 2465BDM has GPIB. |
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Having just done so, I can most definitely say you can back up/dump the NVRAM via GPIB, and supposedly reload it too. Certainly it's not a substitute for a re-calibration if the NVRAM goes bad, but for the home hobbyist it's more often than not "good enough" even if it's a couple years out of date. And it's good insurance when you are poking around inside your scope.
There's an EEVblog thread on the topic of dumping calibration for the 2400 series. I have a printout in the back of my SM, but lost the URL. After you've connected via GPIB: -Unblock the commands by sending "KEY 0" -Dump your data with "EAROM? <addr>" where addr is 0...255 you can do a csv list, e.g. EAROM? 0,1,2,3, but one at a time is a little more convenient for reasons that will become apparent. - The scope will reply with "EAR <addr>:<value>" (list of items if multiple addresses). Value is decimal. For example: "EAR 0:1279" - Writing values back is done with "EAROM <addr>:<value>". Apparently multiple values on one line does not work, so if you have individual lines from the above, it's far easier to parse and load back in. There's also a comment in the thread musing about a way to possibly enter values directly on the scope via Exerciser 2. I'd not be surprised if this was the case with a magic key sequence, as the EAROM? query alters the pointer for the exerciser. For example, if I open EXER 2 to 0x00 and then do an EAROM? 32 query, and then push the address +1 key, the shown address jumps to 0x21. I bought a cheap PCI GPIB card off ebay for a couple Hamiltons. |
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Chuck Harris
Ok, That's interesting to hear.
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I had no doubt that you could dump the codes, as you can dump every byte from the NVRAM, if you want to... but putting them back eluded me of late. About 25 years ago, I found out how to do both with the 2465, but I forgot how, and couldn't find my notes... there have been several moves since that time. Your mention of using EXER2 in conjunction with EAR read sounds familiar. I have calibrated, uhmnn, cough, cough, several of these scopes, and it seems that if they are in regular use, they are significantly off by 5 years. If they just sit in a cabinet, they seem to hold their calibration forever. You can't know which scope you have, unless you have owned it from the beginning (I have one of those), so you have to assume that it needs calibration long before the NVRAM goes dead. The "A" model, and early "B" models could lose calibration from an unfortunate short circuit, but none of the others can. -Chuck Harris uniacke1 via Groups.Io wrote: Having just done so, I can most definitely say you can back up/dump the NVRAM via GPIB, and supposedly reload it too. Certainly it's not a substitute for a re-calibration if the NVRAM goes bad, but for the home hobbyist it's more often than not "good enough" even if it's a couple years out of date. And it's good insurance when you are poking around inside your scope. |
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Hello all, the NVRAM Dallas 1225 in 246xB can be easily removed from the PCB and a machined pin low profile 28 pin socket installed.
The TL 866 PROM programmers are available from China on epay about $40, USB. But very slow shipping. Look for MiniPro TL866 universal programmer. With one of those I have read and written the 1225 NVRAM and loaded default images But I doubt if the GPIB on optioned scopes can access the NVRAM. Just an old timer's rumbling, Jon . |
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Chuck Harris
It is like this:
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Calibration solves multiple issues. Done to its logical conclusion, it makes all of the measurements made by your scope consistent (to within the scope's uncertainties) with every other lab in the world. Less rigorously done, it can make it consistent with all of the test equipment in your lab... assuming that you use that test equipment to calibrate the calibration equipment that calibrates your scope. You need only the loosest connection to NIST and the world to make your scope perform with fidelity, in as far as transient response, trigger response, CRT behavior, focus/hidrive focus, rotation, linearity of display, jitter of readouts, DAC calibration, .. power supply ripple, and voltages, and many other things I forget at the moment. If you want to know what it costs to get it done, not traceable to NIST, but better than tek's specifications, contact me off group. It is way less than the cost of buying all of the necessary equipment. -Chuck Harris uniacke1 via Groups.Io wrote: Interesting. But not entirely surprising given that components will age and wear in. |
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The eevblog post that talks about NV memory access from the GPIB port is here:
Since that post, full backup and restore has since been shown to work on all the 24x5 series (plain, A, and B). As far as I know no one has written a program that uses the method, but it can be done manually fairly easily via any generic utility that can submit GPIB commands. I still haven't found a way to write to NV memory using only the on-screen service menus. I only suspect it might be possible via an undocumented sequence, but haven't worked through enough of the disassembled code. -mark |
Jean-Paul
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