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Communication with Emerson PLC devices

American company Emerson (www2.emersonprocess.com) manufactures meters, sensors and also Smart Wireless Gateways. This device creates a Wireless network that can be used for reading data from meters connected to such network and then pass the data forward via OPC or Modbus protocol for furher usage.

Communication by Modbus protocol - Smart Wireless Gateway

The Smart Wireless Gateway device supports communication by the Modbus protocol.
 
This protocol is not set in the device as default. Therefore it is necessary to enable this protocol before the communication starts. For this communication in the PROMOTIC system can be used: PmModbusMr - Driver for communication by Modbus Master protocol.
For this driver, it is recommended to set the configurators:
- PmCommData > Parameters > Special Parameters > Area base addresses:
- base address "Bo = Coil/output bits" = -1
- base address "Bi = Input bits" = -1
- base address "Ro = Holding/output registers" = -1
- base address "Ri = Input registers" = -1
- PmCommData > Parameters > Special Parameters > Max.number of variables received in one message:
- max.number "Bo = Coil/output bits" = 64
- max.number "Bi = Input bits" = 64
- max.number "Ro = Holding/output registers" = 32
- max.number "Ri = Input registers" = 4
 
The Modbus registry address of analogue values starts at 40000 (based on the documentation). However in reality these values are available at 0 address and higher. For example the value on Modbus registry address 40010 reads in the PROMOTIC system from address 10.
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