I have never used checksum for any device I've programmed. I always assumed the data I was programming was correct and insured that devices I programmed matched that data. If I needed to check for file transmission errors, I'd use something like MD5. The software I use for my hobbyist programmers calculates a checksum, but the algorithm isn't described. I have source for an early version of the program, but was never inclined to check the algorithm because it wasn't a feature I cared about.So you never had any issues with the check sum verification when using different universal programmers? or they all the same for the check sum verification
If it isn't in the documentation, you can put a scope on VCC while the programmer is operating to see if you can see any changes, or you could put a peak detector on the supply if it's changing too quickly, slowly, or you can't get the signal to sync.Some universal programmers are Closed Loop verification and others are Open loop verification, any way to tell?
most techs i saw dont entertain lamentation to this degree they fizzle the thing in a sec or toss it.I never said I did, that is why i'm trying to learn the correct way of erasing, reading, writing, checksum . etc. about EEPROM chips and ERPOM chips.
Most technicians I have worked with don't know either it seems.
dl324 is teaching and training me the right way because of issues i have been having.
What kind of peak detector did you use or did you make one?a peak detector on the supply
i saw a few flaky pics havw one in working circit which first driftts then hangs or self resets. all the time its powered up.EPROMs and EEPROMs are either good, bad or flaky.
If the chip is good, your circuit may work if everything else is ok.
If the chip is bad, your circuit will fail to work.
If the chip is flaky, your circuit will work sometimes and fail sometimes.
Without knowing what is programmed on the chip there is no way your programmer will tell you if the chip is good or bad, checksum or no checksum.
A programmer cannot diagnose a bad chip, exceptions noted below. The only thing you can do is to copy the contents of a good chip on to another good chip.
If the programmer fails to verify a blank chip then the chip is bad.
If the programmer fails to verify the contents written to the chip, then the chip is bad.
You can also read the chip at low, nominal, and high VCC and compare the data. Any charge loss issue should manifest itself; unless charge loss is too severe. If you can acquire the data from another source (e.g. backups or other devices), you can load the correct data into the programmer and do a program verify.If the programmer fails to verify a blank chip then the chip is bad.
If the programmer fails to verify the contents written to the chip, then the chip is bad.
The primary failure in EPROMs/EEPROMs is oxide failure. Writing creates high local electric fields and causes oxide defects to develop. These can trap charge and affect the ability of a bit to be erased. Oxide can also breakdown which affects the ability to hold charge. Other logic is subject to the same failure mechanisms as other CMOS/NMOS devices (oxide failure, ESD, etc).What did the EPROM chips and EEPROM chips failed from in your past experience? any common failures
Just a modified voltage follower.What kind of peak detector did you use or did you make one?;
The hold function would only capture peak if the button was pushed when the signal was at peak. Otherwise, it just holds the reading that was being displayed when the button was pressed.[/quote]Mostly I use the "Hold function" on my DVM meter for a peak detector not sure If this is correct what i am doing.
It is known practice to read back and verify ROMs at higher voltages to detect marginal programming. I think this is beyond the scope of what the TS is looking for.You can also read the chip at low, nominal, and high VCC and compare the data. Any charge loss issue should manifest itself; unless charge loss is too severe. If you can acquire the data from another source (e.g. backups or other devices), you can load the correct data into the programmer and do a program verify.
Not to nit pick, but some ROMs are fuses or are "masked" (manufactured with a certain data pattern).It is known practice to read back and verify ROMs at higher voltages to detect marginal programming.
Seemed to me that the OP was interested in increasing his knowledge. Just my opinion, I could be wrong...I think this is beyond the scope of what the TS is looking for.
Yes I am interested in increasing my knowledge and hope others will read this and help other members alsoSeemed to me that the OP was interested in increasing his knowledge. Just my opinion, I could be wrong...
In circuit test/program capability needs to be designed in. Otherwise, you need to remove the chips to test. If you try to power an EPROM to test it in circuit, you'll power up the rest of the board. Even if you disconnect the EPROM power pin from the board, you'll find that any inputs being driven by the EPROM will power up any CMOS logic on the board through the input protection diodes. If you power the board, you'll be fighting other logic for control of the EPROM.It's a way of testing EEPROM and EPROM chips in circuit.
I can't fathom why someone would do that; well, I could, but it would be an end of the world scenario...The schematics didn't use the inverted logic chips , but the repair person swapped them out and used inverted logic chips which the repair person inverted the EEPROM chip.
If I had to invert data, I'd write a program to flip the bits. I'd do the same to reverse addresses, but I really can't fathom why you would ever need or want to do that.How do you invert the EEPROM file code? so the starting address is the ending address
Invert the ROM contents
Invert the ROM entries
eeprom + logic ICs? also weird.There was some circuit boards I have found in my past that have "Inverted the EEPROM code" and used Logic IC chips with inverted inputs or outputs that is why they inverted the code in the EEPROM chips.
The schematics didn't use the inverted logic chips , but the repair person swapped them out and used inverted logic chips which the repair person inverted the EEPROM chip.
How do you invert the EEPROM file code? so the starting address is the ending address
Invert the ROM contents
Invert the ROM entries
This TS will never post a schematic or a brand name or a model number. He wants Universal Truths that apply to All Circuits Everywhere, so there is no benefit to saying which circuit he is talking about.weird thread mixing up EPROM and EEPROM and talking to test EPROM in circuit
you wouldnt mind to post schematic?
There's still a lot of equipment using them. I have quite a few pieces of equipment from the 70's that are still quite useful. If the EPROMs lost their data, that equipment would be useless.EPROMS are out of fashion for quite a while.
because there is nothing? i was thinking, it might become apparent some day.This TS will never post a schematic or a brand name or a model number. He wants Universal Truths that apply to All Circuits Everywhere, so there is no benefit to saying which circuit he is talking about.
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