Properties
Global data communication is used for cyclic exchange of global data via MPI subnets (for example, I, Q, M) between SIMATIC S7 CPUs. The exchange of data is unacknowledged.
One CPU broadcasts its data to all other CPUs on the MPI subnet.
The integrated communication functions are called via SFCs in the user program.
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Communication 4.2 Communication services
SFCs for Global Data Communication
The following SFCs are integrated in the operating system of the S7-400 CPUs:
Table 4-5 SFCs for Global Data Communication Block Block name Brief description
SFC 60 GD_SEND Collects and sends data of a GD packet
SFC 61 GD_REC Fetches data of an arrived GD message frame and enters it in the receive GD packet.
Reduction ratio
The reduction ratio specifies the number of cycles into which the GD communication is broken down. You set the reduction ratio when you configure global data communication in STEP 7. For example, if you set a reduction ratio of 7, global data communication is performed every 7th cycle. This reduces the load on the CPU.
Send and Receive Conditions
Meet the following conditions for communication via GD circuits:
• For the sender of a GD packet:
Reduction ratiosender x cycle timesender ≥ 60 ms
• For the receiver of a GD packet:
Reduction ratioreceiver x cycle timereceiver
< reduction ratiosender x cycle timesender
A GD packet may be lost if you do not adhere to these conditions. The reasons being:
• The performance of the "smallest" CPU in the GD circuit
• Transmission and reception of global data is performed asynchronously at the stations.
When setting in STEP 7: “Transmit after each CPU cycle“, and the CPU has a scan cycle time < 60 ms, the operating system might overwrite a GD packet of the CPU before it is transmitted. The loss of global data is indicated in the status box of a GD circuit, if you set this function in your STEP 7 configuration.
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Communication
4.2 Communication services
S7-400 Automation System, CPU Specifications
4-12 Manual, 11/2006, A5E00850746-02
4.2.7 Routing
Properties
You can access other stations on other subnets with the programming device / PC of your S7 stations. You can use this for the following actions:
• Downloading user programs
• Downloading a hardware configuration
• Performing testing and diagnostics functions
Note
When the CPU is used as intelligent slave, the routing function is only available when the DP interface is set active. In STEP 7, check the Test, Commissioning, Routing check box in the properties dialog of the DP interface. For detailed information, refer to the
Programming with STEP 7 manual, or directly to the STEP 7 Online Help
Requirements
• The station modules are "capable of routing" (CPUs or CPs).
• The network configuration does not exceed project limits.
• The modules have loaded the configuration data containing the latest "knowledge" of the entire network configuration of the project.
Reason: All modules participating in the network transition must receive the routing information defining the paths to other subnets.
• In your network configuration, the PG/PC you want to use to establish a connection via network node must be assigned to the network it is physically connected to.
• The CPU must set to master mode, or
• when set to operate in slave mode, the Test, Commissioning, Routing functionality must be enabled by setting the check box in STEP 7, in the
DP interface for DP slave properties dialog box.
Routing gateways: MPI - DP
Gateways between subnets are routed in a SIMATIC station that is equipped with interfaces to the respective subnets. The following figure shows CPU 1 (DP master) acting as router for subnets 1 and 2.
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Communication 4.2 Communication services
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Routing Gateways: MPI - DP - PROFINET
The following figure shows access from MPI to PROFINET via PROFIBUS. CPU 1, for example 416-3, is the router for subnet 1 and 2; CPU 2 is the router for subnet 2 and 3.
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Communication
4.2 Communication services
S7-400 Automation System, CPU Specifications
4-14 Manual, 11/2006, A5E00850746-02
Routing: TeleService application example
The following figure shows the remote maintenance of an S7 station using a PG as an application example. The connection to other subnets is established via modem connection.
The bottom of the figure shows how this can be configured in STEP 7.
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Communication 4.2 Communication services
Reference
• You can find additional information on configuration with STEP 7 in the Configuring Hardware and Connections with STEP 7 manual
• You can find more basic information in the Communication with SIMATIC manual.
• You can find additional information about the TeleService adapter under article ID 20983182 on the Internet at http://support.automation.siemens.com.
• You can find additional information on SFCs in the Instruction List.
You can find a detailed description in the STEP 7 Online Help or System and Standard Functions reference manual.