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SkalTura

EEPROM vs. EPROM

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Hi,

 

I'm working on a bankswitch card that supports multigames.

 

I first made a normal 4k multicard using a 27C256 that holds 8 games, for testing purposes. Easy to make, and it worked fine...

Because I have my own programmer, but not an UV eraser, I wanted to use a 29F010 EEprom that can be electrically erased. The pinout of this is (almost) the same as a 27C010. So I copied a few ROM's together and programmed the EEprom, but for some reason that didn't work on my Atari 2600. I used my programmer to read back the ROM file out of the chip, and tested it in Stella (32 in 1). That worked fine, so there doesn't seem to be anything wrong with programmed chip.

 

Does anyone here have any experience using EEproms for DIY cartridges or mulitgame card, and what is the difference between using a EEprom and a normal Eprom (because the normal Eprom is working fine).

 

Many thanks !!

Edited by SkalTura

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I don't have a circuit drawing, but basically it's just A0-A11, and D0-D7 directly from the connector to the EEprom. A12 from the connector to an inverter input, and the inverter output to the CE. The OE is connected to ground. Then I have A12-16 from the EEprom for selecting games. These are connected to +5V, and I used pulldown resistors to ground for every line (47k). By disconnecting the +5V from the A12-A16, and pulling it through the resistors to ground, I can select the different games. And that's it...

 

It works for a normal UV erasable Eprom, but for some reason the 29F010 electrically erasable EEprom doesn't work. The 29F010 has an extra pin (WE - write enable). I tried it connected to ground, and connected to +5V, but in both situations the Atari does nothing with this chip.

Edited by SkalTura

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Yes I did.

 

I also tested the ROM file in Stella as a 32in1 ROM, and that worked fine.

After programming the EEprom, I read back the file and also tested this file in Stella... Also worked.

 

Strange right ?

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I think I had some bad connections on my test board, because after taking my test setup appart, and rebuilding it... it worked with the 29F010B EEprom.

So, now I start testing with bankswitching, and after that a bankswitch multicard.

 

Thanks !!

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