Today’s Modbus installations are becoming increasingly complex. More and more installations are requiring the use of multiple Modbus controllers, and the need to share information between the controllers is becoming increasingly important.
Sharing information between Modbus controllers can be relatively easy if one controller can communicate as a master (or client) and the other as a slave (or server). The master controller simply sends a message to the slave controller and the slave responds. However, what do you do when each controller can only be configured as a master?
The DeviceMaster UP, running with the Modbus Router firmware, provides master-to-master connectivity using a configurable Shared Memory sub-system. The Shared Memory sub-system features eight Holding Register blocks containing 200 registers each, and eight coil blocks containing 160 coils each. Write access for each Shared Memory block can be either enabled for all masters or restricted to a single master. Write messages that are addressed to restricted block(s) from unauthorized master(s) are rejected, logged, and displayed in the Write Violation Log web page.
Additional web pages provide configuration, diagnostics, and status information for the Shared Memory blocks.