S7 Plc

[wglespaul]

What is meant by cross referencing in step 7? What is it used for and how is it done?
Also what are MPI connections?
Thanks

Tom

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Alea Jacta Est

 

[paraffin power]

Cross-referencing shows you where an address is used throughout a program i.e. in which blocks and which network within that block.

MPI connections are normally 3-3 and 8-8.

 

[wglespaul]

Step 7

Thanks for reply on cross referencing.

Is this done with the programmer plugged into a live PLC or can it be done just by looking at the PLC program on the programmer?

Also what does MPI stand for, and what is it used for?
I'm still fairly new to this
Many Thanks,

Tom

 

[paraffin power]

You can generate and view a cross reference without being on-line i.e. just looking at the program.
MPI stands for multi-point interface, I think.
MPI is Siemens' own comms protocol. It can be used to connect two or more PLCs together on an MPI network or connect a PLC to an HMI.

 

[seppoalanen]

What is meant by cross referencing in step 7? What is it used for and how is it done?

Step7 do it itself. In the program view put focus to some variable name (or absolute address) and push the right mouse button. Select 'Go to Location'. Rest part you can see yourself.

Also what are MPI connections?

RS485 based Multi Point Interface. Normally cabling from the CPU can be less than 50 meters without repeaters. Good practice is put repeaters in the PLC cubicle and each Control panel where are OP-panels or where you need outlet for programming.