Is it possible to read-protect / DRM EEPROM chips?

[Delicieuxz]

I've asked someone to read a certain firmware chip for me and send it to me. They're willing to, but they say their reader isn't reading the chip, even though it's supposed to be able to handle the chip. The firmware chip is an aftermarket one with the firmware burned to it by the 3rd-party who sold them the chip. They're wondering if it's somehow copy-protected.

 

Is it possible to implement copy-protection to prevent other people from reading a chip's firmware?

[mariushm]

It's possible for the chip to refuse any read command until a sequence of commands is done or a specific key is sent to a register ... basically a sort of copy protection.

 

It could be the programmer tries to talk to the chip using a frequency that's higher than what the aftermarket supports, a frequency the original/genuine chips were supposed to support.

Or maybe the voltage is too low for the frequency the programmer tries to use. Many possibilities.