Date : Sun, 07 Jun 1992 04:17:40 +1200
From : Dave Sainty <terros@...>
Subject: zip & ram
From: "Mik Davis" <davism@...>:
> A friend of mine wants to make a homebrew sideways RAM from a 62256 chip
> {available from Maplin.} Does anyone know where to get the write enable
> and rom select lines from? I have seen 62256s used in this configuration
> but don't recall how they were wired up ....
Yes, this is what I have done. The 62256 can be used as a 16k ram, but that
would be silly. The first one I made took up two sockets of the 4 (no rom
board), and had diodes stuck on it, but I'de improved on that....
Ok, the ~WE line I have taken from pin 8 on IC77. This is a 74LS00 in the top
left corner of an issue 4 board. It should be consistant on other issues.
This needs to be run to pin 27 on the 62256's. You should probably bend this
pin up so it does not plug into the board...
That is all you need to do for 16k, but you have another 16k to play with...
IC76 houses the rom select latch, and pin12 off this chip (a 74LS163) should be
connected to pin 1 on the 62256's (again, bend te pin up). I forget which line
this is, but I think it is bit 2 of the 4 bit select register.
This means (if you plug the 62256 into socket 3), rom 3 and 11 map to one 16k
bank, and rom 7 and 15 map to the second bank. Without using the rom select,
rom 3, 7, 11 and 15 all map to the single bank of ram.
> Replies to STILESAJ@...
I trust he'll get to read this...
=============
From: julian <julian@...>
>I have placed the BFM archiver on shiraz in *EXECable format, in the
>incoming software direcory. I have also placed version 1.2u of Dave's
>comms package "Tequilacomm", which is archived using BFM, at his
>request.
Thanks Julian.
=============
From: RWF Whitehand <R.W.F.Whitehand1@...>
>I know the original is written in fairly serious C, but I don't suppose
>anyone has done ZIP or unZIP for the beeb, by any remote chance?
I've written UNZIP. I intend to write ZIP. Do people want me to put what I
have done so far on shiraz?