EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: IvoS on August 11, 2013, 11:27:50 am
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I have 27C64A memory, I think it's made by National Semiconductors. I need to make a clone of it. Can I use a memory from different manufacturer? Like ST? Are these memory pin and voltage compatible? Thanks.
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Pinouts are JEDEC-standard, programming algorithm and speed may vary depending on the part.
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Yes, but make sure that the new EPROM has the same or a lower access time then the old one. The naming is 27C64A-<time>, e.g. 27C64A-15 for 150ns. And as amyk already wrote, select the correct type in your programmer software.
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You may consider a flash EEPROM instead, a 28C64 will behave the same for read applications and is cheaper than a windowed EPROM.
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You may consider a flash EEPROM instead, a 28C64 will behave the same for read applications and is cheaper than a windowed EPROM.
Is that 28C64 pin and voltage compatible? The same?
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Is that 28C64 pin and voltage compatible? The same?
Basically - for readin -
You can use just about anything that has the same pinout and voltage. There are many OTPs (even cheaper) or Flash
EEs etc that would work and are available in 5V. As been noted - as long as they are at least as fast. You will need to
check the specs though, just in case you've picked a slightly "odd" one.
Erasing / writing is a whole different thing, but if you're ONLY doing that manually, then who cares.
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If procuring this small of EPROM is difficult, you can go up to 27C256, just make sure the unused address pins are grounded on your PWB. Maybe 27C512 if you your programmer supports the Pin1 change from Vpp to A15. Also check, maybe other address pins were connected, and you can use the larger eprom space if needed.
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Heres a project where a 27C64A and a 27C256 is used on the same board,jumpers are used to switch between them.Also the later version was stacked.
http://www.dos4ever.com/8031board/8031board.html#appendixF (http://www.dos4ever.com/8031board/8031board.html#appendixF)