(continued) Global Data service The Global Data service performs data exchanges in real time between stations belonging to the same distribution group. It is used to synchronize remote applications, or to share a common database between a number of distributed applications. Exchanges are based on a standard producer/consumer protocol, guaranteeing optimum performance with a minimum load on the network. This RTPS ( Real Time Publisher Subscriber ) protocol is promoted by Modbus-IDA ( Interface for Distributed Automation ), and is already a standard adopted by several manufacturers.
A maximum of 64 stations can participate in Global Data within a single distribution froup. Each station can: b Publish one 1024-byte variable. The publication period can be configured from 1 to n processor master task (Mast) periods. b Subscribe to between 1 and 64 variables. The validity of each variable is controlled by status bits (Health Status bits) linked to a refresh timeout configurable between 50 ms and 1s. Access to an element of the variable is not possible. The total size of subscribed variables amounts to 4 K contiguous bytes. To further optimize the performance of the Ethernet network, Global Data can be configured with the multicast filtering option which, together with switches in the ConneXium range, broadcasts data only to Ethernet ports where there is a Global Data service subscriber station. If these switches are not used, Global Data is sent in multicast mode to all switch ports.
Global Data service diagnostics
The diagnostic screens use a colour code to show the Global Data status: b Configured/not configured/faulty. b Published/subscribed. Global Data service diagnostics can be performed in one of five ways: b Via the application program from a specific PLC data zone. b From the setup software debug screen. b From the PLC system diagnostic function displayed by means of an internet browser on a PC station. b Using standard SNMP manager software.
Modicon M340 automation platform
Ethernet Modbus/TCP network
Ethernet Modbus/TCP communication services
Modicon Quantum Modicon Premium Modicon M340
Distribution group 1
Data exchange 4 KB max.
Distribution group 2
IP multicast 22.214.171.124 IP multicast 126.96.36.199 Ethernet Modbus/TCP
Processors: page 1/8 Ruggedized Modicon M340 modules: page 3/2
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