Proline Promag 53 MODBUS RS485 Operation
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5.5 MODBUS RS485 communication
5.5.1 MODBUS RS485 technology
The MODBUS is an open, standardized fieldbus system which is deployed in the areas of
manufacturing automation, process automation and building automation.
System architecture
The MODBUS RS485 is used to specify the functional characteristics of a serial fieldbus system with
which distributed, digital automation systems are networked together.
The MODBUS RS485 distinguishes between master and slave devices.
• Master devices
Master devices determine the data traffic on the fieldbus system. They can send data without an
external request.
• Slave devices
Slave devices, like this measuring device, are peripheral devices. They do not have their own
access rights to the data traffic of the fieldbus system and only send their data due to an external
request from a master.
a0004398
Fig. 43: MODBUS RS485 system architecture
1 MODBUS master (PLC, etc.)
2 MODBUS RS485
3 MODBUS slave (measuring devices, etc.)
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