The symmetry of things

J

Thread Starter

Jiri Baum

Hello,

At the risk of starting another nomenclature war :)

What is the difference between an I/O driver and a Logic Engine?

It seems to me that, from the point of view of the SMM, the situation is
perfectly symmetrical.

The value of each point is provided by exactly one module; for inputs, this is an I/O driver, for outputs and internal relays it's
a Logic Engine (either a particular one, or by semaphore).

Each point is read by any module interested in it; for inputs and internal relays, it's the Logic Engine(s). For outputs, it's an I/O driver in addition to the Logic Engine(s).

Forces are applied just before a point is read, whether it's an input, output or internal relay.

A "traffic cop" installation doesn't need a Logic Engine at all: the I/O drivers will exchange data without any prompting.


Is this as elegant as I think it is?

(Well, you can't stick the persistent internal coils into it the way I've been suggesting. But that's not so important.)

Jiri
--
Jiri Baum <[email protected]>
On the Internet, nobody knows if you are a @{[@{[open(0),<0>]}-1]}-line
perl script...

_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
J

Johan Bengtsson

I agree, except for perhaps one small point, forces:
A force is, as I see it, something you apply to the (physical) I/O, that is - the I/O handler should apply the force. This is not however something I am going to fight for....


/Johan Bengtsson

----------------------------------------
P&L, the Academy of Automation
Box 252, S-281 23 Hässleholm SWEDEN
Tel: +46 451 49 460, Fax: +46 451 89 833
E-mail: [email protected]
Internet: http://www.pol.se/

_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
[email protected]:
> I agree, except for perhaps one small point, forces: A force is, as I see
> it, something you apply to the (physical) I/O, that is - the I/O handler
> should apply the force. This is not however something I am going to fight
> for....

You can just as easily apply it in the core - it'll get to the physical I/O quickly enough, and it lets you apply forces to internal coils.

Applying forces to internal coils is probably one of those things you can't imagine a use for, because you've never had it before, but won't be able to imagine working without once you get used to it :)


Jiri
--
Jiri Baum <[email protected]>
On the Internet, nobody knows if you are a @{[@{[open(0),<0>]}-1]}-line
perl script...

_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
S
On Thu Jan 20 19:09:39 2000 Jiri Baum wrote...
>
>[email protected]:
>> I agree, except for perhaps one small point, forces: A force is, as I see
>> it, something you apply to the (physical) I/O, that is - the I/O handler
>> should apply the force. This is not however something I am going to fight
>> for....
>

I however am willing to fight for putting it in the I/O scanner(s).
It's the "right place" (tm).

--
Stan Brown [email protected] 843-745-3154
Westvaco
Charleston SC.

_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
> >[email protected]:
> >> I agree, except for perhaps one small point, forces: A force is, as I
> >> see it, something you apply to the (physical) I/O, that is - the I/O
> >> handler should apply the force. This is not however something I am
> >> going to fight for....

Stan Brown:
> I however am willing to fight for putting it in the I/O scanner(s).
> It's the "right place" (tm).

But you can't force internal coils from there.


Jiri
--
Jiri Baum <[email protected]>
On the Internet, nobody knows if you are a @{[@{[open(0),<0>]}-1]}-line
perl script...

_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
Top