From: "Fredk" <arcadexpo@mchsi.com>
Newsgroups: rec.games.video.arcade.collecting
Subject: Re: Bank switching on ROMs
Date: Wed, 10 Dec 2003 22:23:05 GMT


I take a shot at trying to explain this (and I am sure some will follow
up with what I missed or correct me ;)

From what I gather your 2 separate games that both occupy a 27c256.

Now you want to bank switch between these 2 games in one rom so yes then a
27c512 is a good choice.

You would combine both these images into a continuous file and burn them into
a 27c512.

Now to bank switch you would pull the highest address line low to access the
first program and pull it high to access the second (high region) program.

On most of the eproms the program enable gets pulled high (+5) for normal
use (non-programming mode), but check the eprom datasheet to be sure.

If you used a 27C010 you would actually have 4 banks to switch between not
3. You would use the 2 highest address lines to make a 1 of 4 choice.


00 = bank 1
01 = bank 2
10 = bank 3
11 = bank 4

Hope this helps a bit.

Fred


"A. Cassady" wrote in message
> Hi.
>
> I want to set up a game so I can flip a switch and change it's region.
> It uses a 27C256 chip for the region rom, and I'd like to use either a
> 27C512 or 27C010(there are three different regions, though I wouldn't
> mind only being able to switch between two) with the last address pin(s)
> connected to a switch to change banks.  My questions:  Do the address
> pins need to be connected to GND or to +5 to switch banks?  Is it
> necessary to connect the program enable input to voltage for the chip to
> function?(It is one of the pins which will not be in the board's socket,
> in the case of the 27C010)
>
> -Andy C