Date   : Sat, 29 Oct 2005 18:46:08 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: (BBC-Micro) Possible EPROM???

"A. J. Davis" <mail@...> wrote:
> >The 27C512-90 is a 64k x 8 bits 90ns CMOS EPROM with a
> >
> I have some AMD 27C512-120 which work ok.
> 
> The only thing to remember is to put your ROM file at the 'end' of the
> EPROM.  So, if you have a 16k ROM image the first 48k must be blank.
> This is what I found when putting a 16K Wordwise image onto a 32k chip
> anyway.
 
Sometimes you have to duplicate the image, so at each 16K offset
you have the same contents.
 
If it's a 28-pin package with standard EPROM pinouts, then it's
quite likely to work. The crucial question is what pin(s) A14 and
A15 are on, and what signal level the Master has on that pin.
 
The Master has one 16K socket and four 32K sockets, so you could
program it with two 16K ROM images. I have done this with 32K
EPROMs with the Compact and BBC B. With the BBC B you can use a
flying lead from the EPROM to collect the extra address line.
Seacrh the archive for something like "BBC 32K ROM". My main BBC
has six sideways ROMs in it:
 
16K BASIC
32K HADFS + Z80BASIC
32K DNFS + VIEW
16K RAM
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
There are three food groups: brown, green and ice cream.