[Visual-devel] Re: [MAT-devel] visual PLC drivers

[Thomas H. <Tho...@we...>]

mat...@li... schrieb am 12.02.04 14:57:28:

Hello,

>Jiri:
> >as far as visual is concerned, what's the situation with MatPLC taking
> >advantage of visual's PLC drivers=3F Can that be done with the existing
> > code,

>Thomas Hergenhahn:
>> I don't know whether this can be done with the existing code in mat as,=
 I
>> did not download recent code for quite a while. But I also think this i=
s
>> not the way to go: The drivers are shared objects, but they heavily rel=
y on
>> VISUAL's "infrastructure".

>Right. It just seems a duplication to have separate drivers in the two=20
>projects...

>> sequences) to and from the PLCs and to close the connection.

>I think we have libnodave on our to-do list, but nobody's got around to i=
t=20
>yet. (Unless you'd be willing to interface it to the MatPLC=3F)
Ok, I consider this.

>> See also my remarks on this subject in:
>> http://www.control.com/1026183428/index=5Fhtml

>Yeah, that whole thread is interesting. Getting a unified driver interfac=
e=20
>would be very good.

>> I should like to suggest that you might use these functions to interfac=
e
>> with matPLC. For VISUAL, I plan to modify PLC drivers in a way that the=
y
>> rely on library routines providing above described functionalty.
>> This means also that I'm prepared to provide the protocols for the othe=
r
>> PLC families supported by VISUAL in similar libraries. My problem is th=
at I
>> do not have different PLCs from each manufacturer to testwith.

>The other possibility would be to migrate all the drivers to one project =
or=20
>the other, and interface the two together.=20
I don't think so. What I tried to say in the above mentioned thread on con=
trol.com and what I tried=20
in designing the interface of libnodave is to design it for general purpos=
e useful to many more=20
projects.
>For instance, if the drivers were=20
>migrated to the MatPLC, the VISUAL server would link against the matplc=20
>library instead of loading the PLC drivers.
In VISUAL it is not THE library, but shared objects for each PLC type, bec=
ause most users will not=20
need more than one while the total number of supported PLCs may (hopefully=
) reach hundreds=20
(Seeing the lists of other SCADA vendors...).

>(The MatPLC points are named rather than having a dev/subdev/area/offset=20
>structure,
This structure doesn't reflect VISUAL's side, but is meant as a superset o=
f the supported PLC's=20
addressing scheme. In addition to these items, there are an area number an=
d a transport method.

"device" one of multiple physical units on a common interface
GE Fanuc: SNP address
Allen Bradley: Data Highway node number
Siemens: MPI address
modBus: not used, possibly IP address

"Subdevice" would address a part(rack,slot) in the device.
Not yet used =3F
modBus: modBus unit ID

"Area " addresses a type of memory where addresse begin from start:
GE Fanuc: M,R,AI,AQ etc. memory areas
Allen Bradley: Area type is (N,F,...) but is not really evaluated.
Siemens: Data , Flags, or Input/Output,
modBus: not used

"Area number"
GE Fanuc: not used
Allen Bradley: File number
Siemens: Data block number in case of data.
modBus: not used

"Transport method"
GE Fanuc: "R" for read or "W" for write
Allen Bradley: A valid combination of CMD and FNC codes, e.g. "0xF 0xA2"
Siemens: "R" for read or "W" for write.
modBus:  codes 3,4,15,16 if I remember right. Ok, they determine areas her=
e also (registers, input=20
registers) but its easier like this, because the library doesn't need to k=
now about them.

> but otherwise it's fairly similar to your proposal. There's a=20
>couple of extra functions to ensure that a bunch of values all come from =
the=20
>same scan and to let the library limit your scan rate, but that's it. All=
 up,=20
>it's seven functions to call.)

>Possibility three is the DAIS thing, which is pretty much the equivalent =
of=20
>OPC, but it's a bit heavy-weight for our purposes. Eventually we'll need =
DAIS=20
>anyway, but for communicating over the network, not for local interface.
I don't know that.

Thomas


=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=
=5F=5F=5F=5F
Extra-Konto: 2,50 %* Zinsen p. a. ab dem ersten Euro! Nur hier mit 25
Euro-Tankgutschein & ExtraPr=E4mie! https://extrakonto.web.de/=3Fmc=3D021110