Using 2 S7 CP342-5's

[maico]

Hi Ali,
I'm setting up comms between DeltaV as master and S7300 cpu315-2 as slave. I have already comms using 1 cp342-5 bet this not enough is it possible to add a second cp342-5 and if so is there much to change in the program.

Thx

 

[JesperMP]

It is possible to a another CP342-5.
But tell us a bit more about why it is not enough with 1 CP342-5.

 

[maico]

Hi Jesper,
My understanding is that you can only transfer 240 bytes in and 240 bytes out when the cp342-5 is being used as a slave. At the moment I have already reached this limit and need to transfer quite a lot more data and I was looking at the options and what I could see was to add another cp342-5. Any input would be grateful.
Thx

 

[JesperMP]

Yes, that seems to be a hard limit.
I think that 244/244 bytes is the limit for DP slaves in general.
You could add another CP342-5, or you could a DP/DP coupler to the DP port on the CPU as master.

 

[maico]

Thx Jesper,
What way do you think is the most robust and straight forward as I already have 1 cp342-5 in place and working adding a DP/DP coupler what extra capacity will that give me?

Thx

 

[JesperMP]

A DP/DP coupler will give you 244/244 bytes.

Is the Deltav system some kind of SCADA ?
If so, to use Profibus master/slave comms is an odd choice.
There are limitations which you have found, and there are advantages that are unnecessary for a SCADA.

 

[mk42]

Is the Deltav system some kind of SCADA ?
If so, to use Profibus master/slave comms is an odd choice.
There are limitations which you have found, and there are advantages that are unnecessary for a SCADA.

Agree with what Jesper is saying.

What kind of update rate do you need between the S7 and DeltaV? If DeltaV needs all data every 50 ms, then maybe Profibus is the right move. If update rate is greater than 100ms, or data is only needed on demand (acyclic), then another driver (S7 Comms) would be preferable (if it exists on the DeltaV side).

It may be easiest to add some Ethernet, and an OPC server, if the DeltaV can't natively do acyclic comms to the S7.