From 35dca04ec982ded9ec07bf8bd1720f0f167dcd69 Mon Sep 17 00:00:00 2001 From: Virgil Dupras Date: Sat, 12 Dec 2020 10:47:30 -0500 Subject: [PATCH] doc/sms/at28: add note about CE-inhibit jumper --- doc/hw/z80/sms/at28.txt | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/doc/hw/z80/sms/at28.txt b/doc/hw/z80/sms/at28.txt index a0b13ec..d68ca68 100644 --- a/doc/hw/z80/sms/at28.txt +++ b/doc/hw/z80/sms/at28.txt @@ -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 hardware or software (I try a lot of dangerous stuff on my 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.