Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ucsd!swrinde!zaphod.mps.ohio-state.edu!wuarchive!uunet!mcsun!ukc!acorn!moncam!emmo
From: emmo@moncam.co.uk (Dave Emmerson)
Newsgroups: sci.electronics
Subject: Re: cheap address decode ideas?
Message-ID: <900@marvin.moncam.co.uk>
Date: 1 Oct 90 04:26:53 GMT
References: <28711@nuchat.UUCP>
Organization: Monotype ADG, Cambridge, UK
Lines: 21

In article <28711@nuchat.UUCP>, steve@nuchat.UUCP (Steve Nuchia) writes:
> Given a desire to have N (=5 in this case) I/O port groups
> decoded at arbitrary addresses without using a whole boatload
> of parts?
> [...]
> for the job?  How about a PAL with a few dozen internal
> register bits?
> 

It should be quite feasible, have you thought about using DIL switches
to set the required port addresses, rather than programming them in?
Registers aren't particularly necessary, but you need at least 36 input
pins and 5 outputs this way. Hardwired, it'll go easily into a 16R6/16L8,
a 20 pin device, and you could have 8 configurations programmed into a 
single device costing just a few dollars.

Or you might be able to use an E2PROM, these are quick and simple to
reprogram, but have long access times, typically 120..150nS, so may not
suit your application.

Dave E.