several users use one plc through a computer network

dear friends
I saw an icon in control panel(simatic workstation) that we can set ip address and other
network features I jumped to this conclusion that we can use it for
conecting one pc to a plc that is conected to another pc with pc adaptor.(several users use one plc through a computer network)
does anyone know about it?

From what I know, this is for people working on the same project over Ethernet, it does not mean different people have access to the same PLC over Ethernet.

If you wat access to the same PLC from different PC's there has to be a physical connection from every PC involved to the same PLC, beit over MPI (with an MPI interface in every PC connected to one MPI network) or Ethernet (with an Ethernet communication processor in the PLC).

Kind regards,

I have seen it.

I once went into the field to help a OEM. The OEM had four computers accessing one PLC5 over Ethernet. 2 Programming computers, 1 RSView and one 1 scanning optimizing computer. The limitation seems to be that two people can't edit the same rung which makes sense if you think about it. The RSLogix5 must have a way of locking rungs that are open for edit.

I have done the same thing with GE 90-30. If several users with the same access level connect to the same PLC, it is the first one connected who can modify the logic. Everyone else would stay in read-only mode.

Same thing with Yaskawa works differently. Users A and B are connected to the same PLC (both have full access rights). User A makes an online change in logic and saves it to PLC. User B does not see the change until he tries to change something in the same subroutine too. Then, an attempt by B to save the changes causes the message "The logic was changed by another program" to appear and the saving operation is refused. All B can do now is to close the sub without saving and to re-open it again - with the changes done by A now visible.

The point is, there is nothing uncommon when several clients can access the same PLC. However, each PLC family would act differently when online changes are attempted. At any case, it would be wise to think ahead and to plan some kind of security measures: access levels, passwords, etc...

From what I know, this is for people working on the same project over Ethernet, it does not mean different people have access to the same PLC over Ethernet.

Click to expand...

dear jvdcande
about my question,I thnik working with one plc s7-300 with several pcs is useful when you are teaching plc .
please explain it more clearely .do you mean they(people working in one project) can see others work and complet others program
becouse I am novice please explain more about MPI.
for using several people with one plc(MPI,multiple user interface
)do we need a special cable(for example RS 485) or ...


dear Peter Nachtwey
please explain about OEM .how can we do it