Newsgroups: comp.robotics
Path: brunix!sgiblab!sdd.hp.com!cs.utexas.edu!swrinde!pipex!demon!news
From: markh@rubidog.demon.co.uk (Mark Hodsman)
Subject: Mini PLC language
Message-ID: <18@rubidog.demon.co.uk>
Sender: news@demon.co.uk (Usenet Administration)
Nntp-Posting-Host: rubidog.demon.co.uk
Organization: Wenslyedale Cheese Shops Inc
Date: Mon, 25 Jul 1994 21:51:37 GMT
Lines: 32


I might be out on my own on this one, but....

Having spent some time programming with Basic ,assembler,C and Pascal I have
yet to find a better method of implementing control code than those so called
'ladder logic' or PLC languages found on the industrial machines. 

I have used various flavours, Allen Bradley coming out best. 
Whilst being mostly low level stuff, it is quite straightforward to implement
complex electrical circuits.
(More intuitive than assembler)
Some PLC languages are hybrid, and allow you to enter the logic and then if you
need something fancy ie floating point operations, allow you to drop in to 'C'
or Pascal etc.

I wonder if a 'mini' implementation of a ladder-logic programming language
could be realised?

BTW The Allen Bradley 5 series PLC uses a 68020 and a Z80 handles network
communications, so presumably there's quite a bit of heavy-duty processing
going on to keep the scan times of say, 500 rungs of logic with a few
milliseconds.

I would appreciate anybodys thoughts on the above.

If anyone would like to look at some printouts of a typical ladder-logic
program I would be glad to email them some info.

--
Mark H                         +44 724 762130
Ya pays yer money ya takes yer chances

