Just repaired our fridge when, according to Murphy's law, the next appliance became shaky. Our pellet stove has twice refused to be turned off. Unfortunately, instead of analog it's all buttons that are operated via port pins of a micro controller. Pressing several of those willy-nilly made the on/off button work, at least long enough to turn it off. When the circuit board is cold the botton always works but not when warm after running the stove overnight. The micro controller is a Winbond W78E52BF-24 running on a 12MHz crystal. It is based on what they call electrically erasable MTP-ROM with which I assume they mean EEPROM. Date code is 2001 and that is also when we had that pellet stove installed. Can these things develop loss of flash memory (bit rot) this soon, after only two decades? Any remedy short or reprogramming or is it toast? -- Regards, Joerg http://www.analogconsultants.com/
Bit rot in micro controllers?
Started by ●December 11, 2021
Reply by ●December 11, 20212021-12-11
Joerg <news@analogconsultants.com> Wrote in message:r> Just repaired our fridge when, according to Murphy's law, the next appliance became shaky. Our pellet stove has twice refused to be turned off. Unfortunately, instead of analog it's all buttons that are operated via port pins of a micro controller. Pressing several of those willy-nilly made the on/off button work, at least long enough to turn it off. When the circuit board is cold the botton always works but not when warm after running the stove overnight.The micro controller is a Winbond W78E52BF-24 running on a 12MHz crystal. It is based on what they call electrically erasable MTP-ROM with which I assume they mean EEPROM. Date code is 2001 and that is also when we had that pellet stove installed.Can these things develop loss of flash memory (bit rot) this soon, after only two decades? Any remedy short or reprogramming or is it toast?-- Regards, Joerghttp://www.analogconsultants.com/-- Probably a bad switch or solder connection from thermal cycling. Cheers ----Android NewsGroup Reader---- https://piaohong.s3-us-west-2.amazonaws.com/usenet/index.html
Reply by ●December 11, 20212021-12-11
On Saturday, December 11, 2021 at 2:58:14 PM UTC-5, Martin Rid wrote:> Joerg <ne...@analogconsultants.com> Wrote in message:r > > Just repaired our fridge when, according to Murphy's law, the next appliance became shaky. Our pellet stove has twice refused to be turned off. Unfortunately, instead of analog it's all buttons that are operated via port pins of a micro controller. Pressing several of those willy-nilly made the on/off button work, at least long enough to turn it off. When the circuit board is cold the botton always works but not when warm after running the stove overnight.The micro controller is a Winbond W78E52BF-24 running on a 12MHz crystal. It is based on what they call electrically erasable MTP-ROM with which I assume they mean EEPROM. Date code is 2001 and that is also when we had that pellet stove installed.Can these things develop loss of flash memory (bit rot) this soon, after only two decades? Any remedy short or reprogramming or is it toast?-- Regards, Joerghttp://www.analogconsultants.com/ > > -- > Probably a bad switch or solder connection from thermal cycling.+1` Don't know why the EEPROM would be suspect first. Wouldn't that produce a more permanent glitch? I suppose it could become temperature sensitive. Maybe the stove manufacturer has a note on this issue or even a recall. -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
Reply by ●December 11, 20212021-12-11
On 12/11/21 12:30 PM, Rick C wrote:> On Saturday, December 11, 2021 at 2:58:14 PM UTC-5, Martin Rid wrote: >> Joerg <ne...@analogconsultants.com> Wrote in message:r >>> Just repaired our fridge when, according to Murphy's law, the next appliance became shaky. Our pellet stove has twice refused to be turned off. Unfortunately, instead of analog it's all buttons that are operated via port pins of a micro controller. Pressing several of those willy-nilly made the on/off button work, at least long enough to turn it off. When the circuit board is cold the botton always works but not when warm after running the stove overnight.The micro controller is a Winbond W78E52BF-24 running on a 12MHz crystal. It is based on what they call electrically erasable MTP-ROM with which I assume they mean EEPROM. Date code is 2001 and that is also when we had that pellet stove installed.Can these things develop loss of flash memory (bit rot) this soon, after only two decades? Any remedy short or reprogramming or is it toast?-- Regards, Joerghttp://www.analogconsultants.com/ >> >> -- >> Probably a bad switch or solder connection from thermal cycling. >I don't think so because several other buttons also fail when warm and they aren't set in a matrix. The solder job on the board looks very good and it all ohms out well.> +1` > > Don't know why the EEPROM would be suspect first. Wouldn't that produce a more permanent glitch? I suppose it could become temperature sensitive.That's why I am asking, to see whether this is a sign of impending "permanent" bit rot. I don't know much abou this EEPROM business.> ... Maybe the stove manufacturer has a note on this issue or even a recall. >I doubt they really care about that. There was another issue with this stove right after installation. I really had to rock the boat until they admitted it and actually sent out a correction note to installers with my mod in there (exhaust temp sensor). Worst case I may have to "analogize" the whole enchilada but that would require a lot of reverse engineering and work. Of course, then it would last forever. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●December 11, 20212021-12-11
On Saturday, 11 December 2021 at 15:45:03 UTC-5, Joerg wrote:> On 12/11/21 12:30 PM, Rick C wrote: > > On Saturday, December 11, 2021 at 2:58:14 PM UTC-5, Martin Rid wrote: > >> Joerg <ne...@analogconsultants.com> Wrote in message:r > >>> Just repaired our fridge when, according to Murphy's law, the next appliance became shaky. Our pellet stove has twice refused to be turned off. Unfortunately, instead of analog it's all buttons that are operated via port pins of a micro controller. Pressing several of those willy-nilly made the on/off button work, at least long enough to turn it off. When the circuit board is cold the botton always works but not when warm after running the stove overnight.The micro controller is a Winbond W78E52BF-24 running on a 12MHz crystal. It is based on what they call electrically erasable MTP-ROM with which I assume they mean EEPROM. Date code is 2001 and that is also when we had that pellet stove installed.Can these things develop loss of flash memory (bit rot) this soon, after only two decades? Any remedy short or reprogramming or is it toast?-- Regards, Joerghttp://www.analogconsultants.com/ > >> > >> -- > >> Probably a bad switch or solder connection from thermal cycling. > > > I don't think so because several other buttons also fail when warm and > they aren't set in a matrix. The solder job on the board looks very good > and it all ohms out well. > > +1` > > > > Don't know why the EEPROM would be suspect first. Wouldn't that produce a more permanent glitch? I suppose it could become temperature sensitive. > That's why I am asking, to see whether this is a sign of impending > "permanent" bit rot. I don't know much abou this EEPROM business. > > > > ... Maybe the stove manufacturer has a note on this issue or even a recall. > > > > I doubt they really care about that. There was another issue with this > stove right after installation. I really had to rock the boat until they > admitted it and actually sent out a correction note to installers with > my mod in there (exhaust temp sensor). > > Worst case I may have to "analogize" the whole enchilada but that would > require a lot of reverse engineering and work. Of course, then it would > last forever. > -- > Regards, Joerg > > http://www.analogconsultants.com/Maybe the switch contacts are getting corroded. This happened to my Maytag front loader washing machine. The power switch is directly above the soap tray and gets corroded from the bleach fumes. I put a drop of mineral oil on the button shaft where it worked its way into the switch. After a couple of applications the mineral oil reached the contacts and cleaned them. Now the switch works perfectly with no sign of degredation. I think the mineral oil is protecting the contacts from the fumes.
Reply by ●December 11, 20212021-12-11
On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <news@analogconsultants.com> wrote:>The micro controller is a Winbond W78E52BF-24 running on a 12MHz >crystal. It is based on what they call electrically erasable MTP-ROM >with which I assume they mean EEPROM. Date code is 2001 and that is also >when we had that pellet stove installed. > >Can these things develop loss of flash memory (bit rot) this soon, after >only two decades? Any remedy short or reprogramming or is it toast?MTP-ROM is suppose to be good for up to 1 million write cycles: <https://anysilicon.com/semipedia/multi-time-programmable-mtp-memory-ip/> However, after only 1,000 erase/write cycles, the erase/write voltages begins to change. See Fig 15: <https://onlinelibrary.wiley.com/doi/full/10.4218/etrij.15.0114.1428> "After 1,000 erasing/writing cycles at a program voltage of �6 V with a write time of 5 ms, the VT of a programmed cell is lowered from 2.92 V to 2.9 V and the VT of an erased cell is raised from -1.3 V to -0.5 V." If the MTP-ROM device initially worked properly, and then slowly started failing to recognize button pushes, that might be the problem. Assuming you run the pellet burner for half the year and turn it on/off once per day, that would be: 180 days * 1 cycle/day * 20 years = 3,600 erase/write cycles which might be sufficient to see the problem. Note: I don't have any experience with the Winbond W78E52BF-24. Therefore, I don't know if it has this problem. -- Jeff Liebermann jeffl@cruzio.com PO Box 272 http://www.LearnByDestroying.com Ben Lomond CA 95005-0272 Skype: JeffLiebermann AE6KS 831-336-2558
Reply by ●December 11, 20212021-12-11
On 12-Dec-21 11:14 am, Jeff Liebermann wrote:> On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <news@analogconsultants.com> > wrote: > >> The micro controller is a Winbond W78E52BF-24 running on a 12MHz >> crystal. It is based on what they call electrically erasable MTP-ROM >> with which I assume they mean EEPROM. Date code is 2001 and that is also >> when we had that pellet stove installed. >> >> Can these things develop loss of flash memory (bit rot) this soon, after >> only two decades? Any remedy short or reprogramming or is it toast? > > MTP-ROM is suppose to be good for up to 1 million write cycles: > <https://anysilicon.com/semipedia/multi-time-programmable-mtp-memory-ip/> > However, after only 1,000 erase/write cycles, the erase/write voltages > begins to change. See Fig 15: > <https://onlinelibrary.wiley.com/doi/full/10.4218/etrij.15.0114.1428> > "After 1,000 erasing/writing cycles at a program > voltage of ±6 V with a write time of 5 ms, the > VT of a programmed cell is lowered from 2.92 V > to 2.9 V and the VT of an erased cell is raised > from -1.3 V to -0.5 V." > If the MTP-ROM device initially worked properly, and then slowly > started failing to recognize button pushes, that might be the problem. > Assuming you run the pellet burner for half the year and turn it > on/off once per day, that would be: > 180 days * 1 cycle/day * 20 years = 3,600 erase/write cycles > which might be sufficient to see the problem. > > Note: I don't have any experience with the Winbond W78E52BF-24. > Therefore, I don't know if it has this problem. > >It doesn't seem likely that the system is writing its flash every time it is turned on, or off. Indeed, it doesn't sound like it has a reason to write its flash at all, with flash being used merely because it was cheaper than getting a custom ROM. Sylvia
Reply by ●December 11, 20212021-12-11
On Sun, 12 Dec 2021 11:26:42 +1100, Sylvia Else <sylvia@email.invalid> wrote:>On 12-Dec-21 11:14 am, Jeff Liebermann wrote: >> On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <news@analogconsultants.com> >> wrote: >> >>> The micro controller is a Winbond W78E52BF-24 running on a 12MHz >>> crystal. It is based on what they call electrically erasable MTP-ROM >>> with which I assume they mean EEPROM. Date code is 2001 and that is also >>> when we had that pellet stove installed. >>> >>> Can these things develop loss of flash memory (bit rot) this soon, after >>> only two decades? Any remedy short or reprogramming or is it toast? >> >> MTP-ROM is suppose to be good for up to 1 million write cycles: >> <https://anysilicon.com/semipedia/multi-time-programmable-mtp-memory-ip/> >> However, after only 1,000 erase/write cycles, the erase/write voltages >> begins to change. See Fig 15: >> <https://onlinelibrary.wiley.com/doi/full/10.4218/etrij.15.0114.1428> >> "After 1,000 erasing/writing cycles at a program >> voltage of �6 V with a write time of 5 ms, the >> VT of a programmed cell is lowered from 2.92 V >> to 2.9 V and the VT of an erased cell is raised >> from -1.3 V to -0.5 V." >> If the MTP-ROM device initially worked properly, and then slowly >> started failing to recognize button pushes, that might be the problem. >> Assuming you run the pellet burner for half the year and turn it >> on/off once per day, that would be: >> 180 days * 1 cycle/day * 20 years = 3,600 erase/write cycles >> which might be sufficient to see the problem. >> >> Note: I don't have any experience with the Winbond W78E52BF-24. >> Therefore, I don't know if it has this problem.>It doesn't seem likely that the system is writing its flash every time >it is turned on, or off. Indeed, it doesn't sound like it has a reason >to write its flash at all, with flash being used merely because it was >cheaper than getting a custom ROM. > >SylviaMaybe you're right. I guess I have to dig deeper. The other symptoms (sensitivity to heat and other inputs having problems) seem (to me) to point to a chip problem. The data sheet indicates that the 8 KBytes of electrically erasable/programmable MTP-ROM is for program memory. <https://www.digchip.com/datasheets/download_datasheet.php?id=1048062&part-number=W78E52B-24> The device also has 256 bytes of scratch pad RAM. Therefore, there is no need to use the MTP-ROM as a non-volatile scratch pad, unless the chip is also doing something write intensive, such as data logging. The chip is capable of addressing up to 64 KBytes of external RAM. If this is static RAM, then it could be used for saving system status when the power is cycles. If it's volatile (dynamic) RAM, it would require a battery. If only a few things need to be stored (auger position, burn time, power status, etc), it could probably be done in the chip's built in 256 byte scratch pad RAM. If most data is being stored, it would be very tempting to save it to the MTP-ROM area. I still like my first guess(tm), but to be certain, I would need to know more about the controller board and what the chip is doing. -- Jeff Liebermann jeffl@cruzio.com PO Box 272 http://www.LearnByDestroying.com Ben Lomond CA 95005-0272 Skype: JeffLiebermann AE6KS 831-336-2558
Reply by ●December 12, 20212021-12-12
On 2021-12-11, Joerg <news@analogconsultants.com> wrote:> The micro controller is a Winbond W78E52BF-24 running on a 12MHz > crystal. It is based on what they call electrically erasable MTP-ROM > with which I assume they mean EEPROM. Date code is 2001 and that is also > when we had that pellet stove installed. > > Can these things develop loss of flash memory (bit rot) this soon, after > only two decades? Any remedy short or reprogramming or is it toast?Quite probably yes - I remember a series of TFT monitors some years ago where that happened to the on-board controller. Raising/lowering VCC may help a bit (if it is not read-protected, you might try to read the memory at different VCC levels and see if you can get correct data, and then re-program). cu Michael
Reply by ●December 12, 20212021-12-12
On 11/12/2021 19:51, Joerg wrote:> Just repaired our fridge when, according to Murphy's law, the next > appliance became shaky. Our pellet stove has twice refused to be turned > off. Unfortunately, instead of analog it's all buttons that are operated > via port pins of a micro controller. Pressing several of those > willy-nilly made the on/off button work, at least long enough to turn it > off. When the circuit board is cold the botton always works but not when > warm after running the stove overnight. > > The micro controller is a Winbond W78E52BF-24 running on a 12MHz > crystal. It is based on what they call electrically erasable MTP-ROM > with which I assume they mean EEPROM. Date code is 2001 and that is also > when we had that pellet stove installed. > > Can these things develop loss of flash memory (bit rot) this soon, after > only two decades? Any remedy short or reprogramming or is it toast?My instinct would be there is a failing electrolytic capacitor somewhere that is allowing the CPU to see glitches that blind it to the on/off button. Some polling algorithms are a bit stupid so another button stuck down might also have the same effect. You might have hoped that there would be a failsafe emergency stop button on something that makes fire! I never trust CPUs for safety interlocks! There is good reason. -- Regards, Martin Brown
