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doc/sms/at28: add note about CE-inhibit jumper

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Virgil Dupras 2020-12-12 10:47:30 -05:00
parent 7dae33ce36
commit 35dca04ec9
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doc/hw/z80/sms/at28.txt
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@ -24,3 +24,11 @@ prototype, I hard-wired the first chip's WE to high because I
never want to write to it, despite bugs I might introduce in never want to write to it, despite bugs I might introduce in
hardware or software (I try a lot of dangerous stuff on my hardware or software (I try a lot of dangerous stuff on my
machines...). machines...).
On top of that, you will likely want to add a physical CE-
inhibit jumper (a jumper hard-wired to VCC) on the AT28 socket.
The reason for this is that if the EEPROM you have on your
socket ends with a SEGA TMR signature, it will be a wrong one,
but it will still be picked up by the BIOS and Collapse OS will
refuse to boot. A CE-inhibit switch that you can remove after
boot will solve the problem.