Apple II Computer Info
#############################################################################
### FILE : genericio.specs
#############################################################################
### Created : Tuesday, November 17, 1998 Modified: Tuesday, November 17, 1998
### File Type: "TEXT" File Creator: "LMAN"
### File Size: 7359 bytes 7 KB
#############################################################################
Newsgroups: comp.sys.apple2
100000@moose> <david.911171291@wraith>
Subject: Re: Hardware Project
Date: Tue, 17 Nov 1998 08:08:37 +1030
Lines: 76
X-Newsreader: Microsoft Outlook Express 4.72.3110.1
X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3
NNTP-Posting-Host: pppk56a-77.mtx.net.au
X-Trace: 17 Nov 1998 08:06:29 -1050, pppk56a-77.mtx.net.au
Path: news1.icaen!news.uiowa.edu!news.physics.uiowa.edu!math.ohio-
state.edu!news.cis.ohio-
state.edu!news.maxwell.syr.edu!newspeer.monmouth.com!intgwpad.nntp.telstra.net!new
s1.optus.net.au!optus!yorrell.saard.net!duster.adelaide.on.net!news.saix.saia.asn.
au!news.mtx.net.au!pppk56a-77.mtx.net.au
Xref: news1.icaen comp.sys.apple2:141876
David Wilson wrote in message ...
>Most any card you design with on-board ROM needs to decode all three
selects
>(DEVSEL, IOSEL and IOSTB) and generate chip selects for ROM, devices and
the
>data bus buffer. This tends to take quite a few LSTTL chips. My idea is to
>replace these with a single PAL/GAL (plus an 8 input NAND gate) to take
care
>of all this (including the CFFF disable function). It will also allow for
the
>use of RAM instead of ROM as this makes code development much easier.
>
>Any thoughts on this would be appreciated.
It is hard to imagine any significant project being undertaken which would
really benefit from this. It is almost impossible to get hold of devices (eg
EPROM) that would fit into the memory space (and those you do get, you
probably wouldn't want to use). Using larger devices would be a waste
without making available the rest of the memory which means using some form
of bank switching.
How generic is the PAL/GAL to be (since you're also adding a TTL device as
well)?
PLDs are becoming inexpensive and readily available. It would be easy enough
to produce a trivial PLD design which would decode everything (get rid of
the NAND gate), provide /CS lines and addressing for modern memory devices
(eg 128Kx8 --> 512Kx8) making the entire space available through the 2K
C800:CFFF window using an arbitrary location (eg C0[n+8]0) for the bank
Apple II Computer Technical Information : Apple II Family Hardware Info
ftp://ground.ecn.uiowa.edu/2/apple2/miscinfo/hardware : May 2001 : 174 of 572
(22 pages)
(16 pages)
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Commentaires sur ces manuels