Data in EPROMs is stored as a charge (electrons) on a floating gate. Over time, those electrons will migrate. When enough of them migrate and the charge on the floating gate will no longer be high enough to be read as being programmed.

If you read the data from such an EPROM at low VCC, that will change the threshold voltage for determining whether a bit is programmed. If you read the data at 4.2V soon enough after data starts reading incorrectly, you can recover the correct data. You can then use this data to program another EPROM.

I have EPROM programmers that allow me to set any voltage I want for reading, programming, and blank verifying. Anyone with equipment capable of reading at low voltage can program one that might work. That's why I asked where you are located. If you're in the US, I can do this.

Iam outside US, my region is Indonesia. Maybe if i sent the program file can you see where the error code will show? And maybe if you can correct the code.

Thanks before

 

Iam outside US, my region is Indonesia. Maybe if i sent the program file can you see where the error code will show? And maybe if you can correct the code.

I'd need the EPROM so I could try reading the data at other voltages to determine what was causing the differences.

 

I'd need the EPROM so I could try reading the data at other voltages to determine what was causing the differences.

I can't send the eprom because it cost so expensive charge, maybe if you can help me with another way

 

Yes.
Read the data at 5V, 4.5V, and 4V. Compare the data read at 4.5V and 5V. They should be different.

Then compare the data at 4V and 4.5V. If they're the same, you can use that data to program a new EPROM.

If the second compare isn't the same, you need to determine which bits are different to see if the cause might be VCC being too low. You could have an EPROM that won't operate at VCC=4V. STM only guarantees to 4.2V (implicitly from their programming algorithm).

This is the programming algorithm for M27C512:
View attachment 194878

Also note that your program can't set the correct programming voltage. STM calls for VCC=6.25V. You might be able to use 6.5V. I never tried because I can set VCC to 6.25V for programming.

I already compare the data from VCC and i think this problem is not from VCC, maybe any problem will cause?

 

I already compare the data from VCC and i think this problem is not from VCC, maybe any problem will cause?

If the data read at 4.5V and 5V are the same, the EPROM isn't the problem or too much charge has been lost to read the correct data at 4.5V.

If there's no way for you to read the data at a lower voltage, you need someone with a more flexible programmer to help you.

You could try to use a schottky diode to drop VCC a few tenths of a volt, but the non-linear voltage drop may cause more problems than it solves.

 

My Yamaha D2040 can't boot, and i check every single component does'nt have any damaged components.

I think its Eprom, but i try to check i can't see where the error.
If any one know machine language, could anyone tell me where the code was corrupted?, i will send the program code that i was read with my devices

 

If any one know machine language, could anyone tell me where the code was corrupted?, i will send the program code that i was read with my devices

It's unlikely that anyone is going to be able to help you by reading the data from the EPROM. We have no idea what the data represents.

Have you done this?

Read the data at 5V, 4.5V, and 4V. Compare the data read at 4.5V and 5V. They should be different.

If the data read at 4.5V and 5V are different, compare the data read at 4.5V and 4.0V. If they're the same, programming a new EPROM with the data read at 4.5V might fix the problem.