Doing the "impossible" with S7 DP comms.

[JesperMP]

Yes it is exactly what you have done allready.

As it seems that it is possible to do it (because the other guy says so), and because we cannot pinpoint where your two previous projects (integrated and standalone) works and doesnt work, I suggest that we start all over again.

Reset both CPUs.
Try to make one project with S7-400 and S7-300 and make a connection between the two in S7-400. Then download to S7-400 only.
Then make another project with S7-300 only and download to S7-300.

If PUT and GET works, then repeat the whole thing with fresh new programs but alter the Profibus addresses.

If it still works, then I guess it can be assumed it will work in general.

 

[PLucas]

Hi Jesper

No problem, I will do that a bit later on today.

You might have noticed from the projects I sent you that I have set the 400 up with a DP address of 4, I have left the 300 at it's default of 2, as I assume that is what your PLC's will be coming in as.

Paul

 

[PLucas]

Jesper

Now I am even more confused/pi**ed off.

I have just reset/deleted both CPU's and again set up a project with the 412 and a 300 in it, networked via DP, compiled it and downloaded to the 412 only!

I then closed this project and opened up a new one with just the 315 in it, exactly the same as before, downloaded this to the 315 only.

I opened up a VAT table, had a look in DB1 in the 315, lo and behold data is being written to it!!

I cannot understand WTF is going on, this is no different from what I tried last week, but now we have comms, last week we didn't! I haven't tried changing the DP addresses yet, the 412 is addressed as 4 and the 315 is 2, I will do that a little later.

I also intent to go through these projects with a fine toothed comb and see if I can 'spot the difference'. I will zip them up and send them to you later on this evening as well.

Paul

 

[PLucas]

Hi Jesper

I didn't have any time to go through the projects yesterday or make any changes to the setup.

This morning I changed the DP address of the 315 from 2 to 10, downloaded this to the 315 only (I didn't make the change in the 412 project), checked for comms and it was as I expected it to be, no data being written. I then made the same change in the 412 project, so that the connection details for the 412 were updated, downloaded this to the 412 and again checked for comms. Comms had been re-established.

It seems that this will work providing you get the correct DP address of the 'partner' CPU.

I am still a bit miffed as to why this didn't work the same way last week. Hopefully, I will have a bit of spare time today to go through all the projects and see why that is.

Paul

 

[JesperMP]

Hi again Paul.

I have studied the integrated and the standalone projects with a magnifying glass, and I have found a difference that maybe is important !

Previously we assumed that there was no difference to downloading the S7-315 project from the integrated or the standalone projects. This is wrong.
In the integrated project STEP7 adjust the DP ports to take the other master into account. In the standalone project the DP port is assumed to be the only master in the network.
If (when configuring the DP port) "DP" profile is selected and you select the "Options" button and then the "network stations" tab, there will some settings you cannot change (they will be greyed out).
But you can see that in the integrated project it will look like this:

DP masters:        2

DP slaves:         0

Active stations..: 2 

In the standalone project it will look like this:

DP masters:        1

DP slaves:         0

Active stations..: 1 

It is possible that is was THIS that caused comms to succeed or fail previously.

I can see two workarounds:
Insert a dummy S7-400 in the S7-300 project.
Or select the "user-defined" bus profile and then add as many active DP masters as you believe will be in the project (like I have done in the screenshot below).
[attachment]

 

[PLucas]

It does work!

Jesper

If you read my reply (3rd post previous to this one), you will see that I had comms with two seperate projects after a memory reset on both CPU's.

As I am not at work today, I can't send them to you yet for you to have a look at. I will zip them up tomorrow and email them to you tomorrow evening from my home PC.

Paul

 

[JesperMP]

Yes, of course I read all your posts So I did see that it did work in the last attempt.

I am just trying to figure out a reason why it didnt work before.

In the last attempts the S7-300 project was completely standalone ("masters" = 1, and "active stations" = 1). So it seems that it can work even with out taking the S7-400 into account in the setup of the S7-300.

But maybe the DP port on the S7-315 can get "screwed up" in some cases, maybe when the S7-400 enters the DP network.
Setting "masters" = 2, and "active stations" = 2 possibly makes the DP port on the S7-300 more fault tolerant.
(Just grasping for any straw that can explain the difference).