S7 download issues: Local MPI address??

Join Date
Aug 2007
Location
Saint Augustine, FL
Posts
178
When downloading, I don't understand what this whole business of setting MPI addressing entails. I dig that the station (this computer) and the PLC should probably have different addresses, but I either get two error messages:

If I put in "2" on the "Select Node Address" dialog, and "1" in the "Set PG/PC Interface" on the properties of the MPI adapter, I get "The set local node address is already in use".

However, if I use anything other than "1" on the MPI adapter, I get a message "The local MPI address for the programming device/PC is higher than the maximum node address or the wrong transmission rate or the wrong interrupt set".

Well, I didn't fool with Transmission Rates or Interrupts, so I deduce that it's address related, but as I discovered, anything other than "1" for the MPI adapter results in that second error message.

Any hints?

Thanks.
 
That's about where I am. The MPI tab is 0, the Select Node Address dialog is 2 (and it shows the correct module type, etc), but i Get "The local MPI address for the programming device/PC is higher than the maximum node address...."

So, perhaps I need to verify transmission rate and interrupt. How do I determine what the current setting is, beyond the Set PG/PC interface (which is currently at defaults).
 
Open the network properties for your project and there should be an image of the plc with a small number next to it. That is the address of the plc. Set the address of the pc to sometuing different (I use 1 for the pc normally).

It is possible to have several plcs and HMI panels on the same MPI network - hence the need for different addresses. I always keep the pc address the same though!
 
What do you know about the PLC your trying to download to. Is it brand new? If it is it should be MPI=2 at 187.5kbps. Set PG/PC should be configured as node address 0 at 187.5. This is the MPI address of the PC. Make sure you have the correct USB or COM port selected for the adapter.

There should be an autoconfigure option in the Set PG/PC interface. If the connected PLC is putting out a different baud rate, ..., it may be able to detect it.

Is there an HMI or anything else connected or just a processor?
 
Manager->Configure Network shows the CPU (300), with two remote racks of IO. The CPU is 1, the racks 2 and 3. So, in Set PG/PC Interface, i tried '4' for the address (then 30s, 185.5kbps, 31), and it gave me the longer "the local is higher" error. Does that mean, I should make the PC #1, and figure out how to make the PLC 2 (then 3,4)? Why isn't #0 working then?
 
What do you know about the PLC your trying to download to. Is it brand new? If it is it should be MPI=2 at 187.5kbps. Set PG/PC should be configured as node address 0 at 187.5. This is the MPI address of the PC. Make sure you have the correct USB or COM port selected for the adapter.

There should be an autoconfigure option in the Set PG/PC interface. If the connected PLC is putting out a different baud rate, ..., it may be able to detect it.

Is there an HMI or anything else connected or just a processor?

Out of the box 300. The PG/PC interface is set to 187.5 at address 0. I'm using USB and it is so set.

No autoconfigure that I can spot.

The only thing this PLC has is two additional racks for IO. They're hooked up with Profi, though technically not at the moment, as the port is taken up with the USB adapter.
 
Just to make sure: If you have downloaded the software (with the bus protocol already set to Profibus) once, you will no longer be able to connect over MPI, so you'll have to set the PC interface to Profibus.

  1. Open 'Set PG/PC Interface'.
  2. Choose the correct interface as MPI interface.
  3. Check the default settings in 'Properties...': Address 0, Timeout 1s, Transmission rate 187,5kbps, Highest station address 31. No need for the PC/PG to be the only master on the bus. Or use the 'Default' button.
  4. Close the Properties and use the 'Diagnostics...' function.
  5. Perform a 'Test'. If the protocol and the transmission rate are correct, it will tell you so. If it doesn't, this is not a brand new PLC, and you'll have to find out which protocol and/or transmission rate is being used.
  6. Once you have tested the network as being OK, you can now use the 'Read' function: It will tell you which participants can be found on the bus.
 
Last edited:
They're hooked up with Profi, though technically not at the moment, as the port is taken up with the USB adapter.

You may be mixing Profibus and MPI. Does the PLC have two ports?

If it does, one is usually MPI and the other is DP. If you've got your adapter configured for MPI and are connecting it to the DP port, it's not going to work.

Connected through the MPI port, you won't see the other modules connected to the DP port, just the processor or anything else connected to the MPI port.

Any address above 31 is too high for MPI. Try setting the Set PG/PC node address back to 0, 187.5, and try to connect through the other port.

You could also configure the adapter for Profibus.
 
Last edited:
tim2 said:
Any address above 31 is too high for MPI.
MPI addresses can be in the range 0 to 126, provided you're not limiting it in the adapter settings. In the adapter you can limit the highest allowed address to 15, 31, 63 or 126 (drop-down list). By default it is limited to 31.

Kind regards,
 
Well, thanks for the help. You pointed me in some good directions and I managed to miraculously get it to work. Sadly, I've fiddled with so many settings, I missed which one was causing the issue, but now the PLC has an IP address, and now I can continue working with it through the TCP network, rather than the USB adapter. :)

Thanks for the help as always. This has got to be one of the best forums on the net for help.
 
The critical info that was never provided: "but now the PLC has an IP address".
Ha ha ha.
So it is a 315-2PN/DP probably.
You do know that you could have done everything from the start via ethernet, dont you ?

It is always nice to get all the critical information up front rather than drip drip.
 

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