Date : Sun, 30 Oct 2005 00:24:42 +0100
From : jgh@... (Jonathan Graham Harston)
Subject: Re: (BBC-Micro) Possible EPROM???
Jules Richardson <julesrichardsonuk@...> wrote:
> > The only thing to remember is to put your ROM file at the 'end' of the
>
> Differences between the typical 272128 (16K x 8) and the 27512:
[snip]
> pin 1 is the strange one, beause I'm surprised the Master doesn't tie
> vpp to 0V for the expected 27128 device (and so for a 27512 A15 would be
[snip]
> and 5V otherwise, then things would work. Or maybe it's a jumper change
> on the Master board?
The Master has the following connections on the motherboard:
SYSTEM ROM4/5, 6/7 ROM8 --------EPROMS-------
IC24 IC37/IC41 IC27 27512 27256 27128
64K/128K 32K 16K 64K 32K 16K
p1 A15 +5v +5v A15 VPP VPP
p27 A14 A14 +5v A14 A14 ~PGM
p22 A16/0v ~OE ~OE ~OE/VPP ~OE ~OE
p20 0v ~CE ~CE ~CE ~CE ~CE
So, presumably, VPP being <12v is seen as "not programing".
A plug-in ROM cartridge could conceivable wire whatever signals it
wants to whatever pin it wants.
There're no jumpers on the Master PCB, only one for the system ROM
to select between a 64K ROM and a 128K ROM.
Hmmm....
Is there such a thing as a 28-pin 128K EPROM with A16 on pin 22? A
271024 maybe? For years I've been meaning to replace the system
ROM with one with my own choice of contents:
MOS MOS 3.20 - fix year in OSWORD 14
ROM F TERMINAL 01
ROM E VIEW 04 - replace with my customised VIEW
ROM D Acorn ADFS 50 - replace with ADFS 1.53
ROM C BASIC 04
ROM B Edit 01 - replace with HADFS
ROM A ViewSheet 02 - replace with ANFS
ROM 9 DFS 79
ROM 8 Acorn ANFS 4.25 04 - now spare
ROM 7 HADFS 05 - now spare
ROM 6 GoMMC 45 - now spare
ROM 5 VIEW 04 - now spare
ROM 4 ? - now spare
ROM 3 Acorn ADFS 53 - now spare
ROM 2 ?
ROM 1 ?
ROM 0 ?
--
J.G.Harston - jgh@... - mdfs.net/User/JGH
Sheffield Boundary Review at http://mdfs.net/User/JGH/Docs/Politics/ParlReview