Description
With OP communication you exchange data between operator stations, for example Operator Panel (OP), Touch Panel (TP) or WinCC, and SIMATIC modules with communications capability. The service is possible by way of MPI, PROFIBUS and Industrial Ethernet subnetworks.

With OP communication we provide you with functions that you need for operator control and monitoring. These functions are integrated in the operating system of the SIMATIC S7 modules. A CPU maintain multiple connections to one or various different operator stations.

When you activate the "Prioritized OCM communication" function you can significantly accelerate the OP communication.

The CPUs below support the "Prioritized OCM communication" function.
 

CPU	Order number	Firmware
CPU315-2 PN/DP	6ES7315-2EH14-0AB0	from V3.2
CPU315F-2 PN/DP	6ES7315-2FJ14-0AB0	from V3.2
CPU317-2 PN/DP	6ES7317-2EK14-0AB0	from V3.2
CPU317F-2 PN/DP	6ES7317-2FK14-0AB0	from V3.2
CPU319-3 PN/DP	6ES7318-3EL01-0AB0	from V3.2
CPU319F-3 PN/DP	6ES7318-3FL01-0AB0	from V3.2

You activate the "Prioritized OCM communication" function for the CPUs above in the Hardware Configuration.
In the Hardware Configuration you double-click the configured CPU to open the Properties dialog. Go to the "Cycle/Clock Memory" tab and activate the "Prioritized OCM communication" function.

Fig. 01

Note

• The consistency of the data to the user program is no longer guaranteed. The consistency must be provided by the user program.
• The cycle time increases.

Data consistency with the PUT/GET functions

• When you activate the "Prioritized OCM communication" function, the specified data consistency is no longer guaranteed, because the communication tags in blocks of up to 240 bytes are not copied consistently to and from the user memory in the cycle control point of the operating system. The communication tags are copied to and from the user memory during the runtime of the user program. The consistency must be provided by the user program.
  The following continue to be consistent:
  • Byte / Word / Double-word access
  • SFC14 "DPRD_DAT"
  • SFC15 "DPWR_DAT"
  • SFC81 "UBLKMOV"
• If a defined data consistency is required, then the communication tags in the user program of the CPUs must not be greater than 240 bytes.

Further Information
The manual "SIMATIC S7-300 CPU 31xC and CPU 31x: Technical Data", sections 3.2.3 and 3.2.11 provide information about the "Prioritized OCM communication" function. The manual is available for downloading in Entry ID: 12996906.

Description
An explanation of the protocols and services for communication via MPI (Multi Point Interface) is available in Entry ID 20982954.

Keywords
MPI bus, MPI subnetwork

Instructions:
In this example, a CP5611 is used for the S7 communication via the SIMATIC NET OPC server to an S7 controller on the MPI bus.

Note:
The procedure described here also applies for communication processors CP5613, CP5511 and CP5512.

General information:
The requirement is that one of the two following configuration tools is installed.

• NCM PC: 
  NCM PC is supplied with the SIMATIC NET CD and permits you to create PC projects and open STEP 7 projects. It is not possible to use this software to edit the S7 blocks in the STEP 7 project.
• STEP 7:
  STEP 7 is a separate software package and permits you to create S7-400, S7-300 and PC projects. It is possible to use this software to edit the S7 blocks.

Only one of these configuration tools can be installed.

Please follow the instructions below for configuring the PC station.

Guide_S7_MPI_e.pdf ( 1741 KB )

Keywords: 
OPC server, S7 connection, MPI, Guideline, Instructions, SOFTNET S7, S7-5613, Set up connection, SIMATIC NET PC software

QUESTION:
How does basic communication work for an S7 CPU with global data and what should I watch out for?

ANSWER:
Global data communication is designed for exchanged small volumes of data. Global data (GD) can be:

• Inputs and outputs
• Markers
• Data in data blocks
• Timer and counter functions

Data exchange is in the form of data packages between CPUs that you can combine into unilateral or bilateral GD rings. A GD ring is identified by a GD ring number.

Unilateral connection:
A CPU can send your GD packages to several CPUs.

Bilateral connection:
Connection between two CPUs: each CPU can send and receive one GD package.

You must make sure that a Receive CPU does not acknowledge the receipt of global data. Communications connections are always required if you want to exchange data via corresponding communication blocks (SFBs, FBs or FCs). By defining a connection you greatly simplify the programming of the communication. The definition is valid of all the communication blocks called and does not have to be redefined each time.

Configuring:
The exact procedure for configuring a GD communication is described in detail in the STEP7 online Help in the SIMATIC Manager.

Attached is a step-by-step guide for configuring a GD communication.
 cp_e12_0_2_e.pdf ( 61 KB )  

QUESTION:  
What are the options for communications via MPI?

ANSWER:  
The following protocols are possible on the MPI bus:

• S7 basic communication
• S7 communication
• Global data communication
• PG/OP communication

Multiple utilities are available for these protocols with different parameters:

1. S7 basic communication

2. S7 communication
   (table does not apply for S7-300, because an S7-300 CPU can only be used as service in S7 communication via MPI.)

* Detailed information on data lengths is available in the manual "System Software for S7-300/400 System and Standard Functions" (chapter 19 - S7 Communication - User Data Size) in Entry ID: 1214574
Table 2: S7 communication

3. Global data communication

For global data communication you can use system functions SFC60 "GD_SND" / SFC61 "GD_RCV" for S7-400.

A master document on communication with SIMATIC S7 is available in Entry ID: 20982954.