I bought a few types of AT28C64b parallel eeproms. Two of these chips failed to work. One was filled with 1's but any attempt to re-write them with a high-to-low transition on WE failed to program the chip. No matter what the data I put in, it never succeeds in programming the memory. The other chip also suffers the same problem except that it was filled with completely random stuff, as opposed to a usual eeprom that's fillled with all ones in it. I don't know if the chips are already dead or their SDP are disabled by the manufacturer. Any thought is appreciated.
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Last Edited: Fri. Jan 12, 2018 - 03:58 PM