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From: rstevew@armory.com (Richard Steven Walz)
Subject: Re: Mini PLC language
Organization: The Armory
Date: Wed, 27 Jul 1994 21:59:50 GMT
Message-ID: <CtMD3s.Dwx@armory.com>
References: <18@rubidog.demon.co.uk>
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In article <18@rubidog.demon.co.uk>,
Mark Hodsman <markh@rubidog.demon.co.uk> wrote:
>
>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
-----------------------------------
I lived and breathed Square-D PLC ladder for a while, teaching it to my
wife when she started a job and found it a steep curve. But I had known a
number of other languages before it. I wasn't impressed. If you want to
pacify old fuds who learned to wire relays and washing machines, it works
fine. But if you can do better, you should. I would say that Forth is
probably the most intriguing language to use for control. It's just that
nobody has ever come up with an agreeable industry standard for primitives
and libraries of base code above the kernel. Everybody has to think they
can make their own better, so it's semi-impossible to document unless you
require it as a condition of payment for your programmers; namely, they
don't get their check till the week's work is DOCUMENTED!! Most other
langauges are still better than ladder! Geez!
-Steve Walz  rstevew@armory.com

