5.0 Communication to PLC
MODBUS Registers and Communication
Modbus RTU is a standard protocol for communication between a PLC / Controller and
slave devices. This section briefly explains the communication with PT2008 Controller
through Modbus RTU protocol. Only the PLC / Controller can make requests to read the
contents of the data registers in the controller. The default slave address of 120 is assigned
at the factory that can be changed by the user as listed in the MODBUS register table
below.
The PLC communication port must be configured as follows
MODBUS
Registers defined in the Wireless Controller
Unit Address:
Default address or ID for the Monitor is 120. To change this address perform a MODBUS
single write register (Function code 6) to register number 3. Write new address to this
register and allow 100 milliseconds before polling with new address. Valid address is
between 1 and 120.
Comm Port
RS-485 (2 wire half duplex)
Baud Rate
9600
Data Bits
8
Parity
None
Stop bits
1
Response Delay
60 msec
Wireless Gas Detection
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