Campbell Scientific LR4 Four Channel Latching Relay Module - Manual (Page 17)

LR4 Four Channel Latching Relay Module
8.2 Modbus Baud Rate
The default baud rate is 19200. Other baud rates are possible. Consult the
factory if other baud rates are required.
8.3 Modbus Mode
The LR4 supports RTU mode only; the ASCII mode is currently not
implemented.
8.4 Modbus Address
The default address assigned to the LR4 is 51. Other addresses can be assigned
to the LR4 by writing the new desired address to register 9999. Once this is
done, the LR4 will only respond to the new address.
If the address is unknown, the broadcast address (0) can be used to set the
address to a valid range (1 - 247).
8.5 Modbus Supported Commands
Read Holding Registers (0x03)
Write Single Register (0x06)
Write Multiple registers (0x10)
8.6 Modbus Operation
All I/O on the LR4 module are treated as registers. The following are the
register assignments for the LR4:
0001 – Relay #1
0002 – Relay #2
0003 – Relay #3
0004 – Relay #4
0005 – External I/O value (currently set as input-only)
0006 – LR4 supply voltage value in mV. 12250 = 12.25 volts
0007 – Signature of the Boot ROM
0008 – Signature of the Operating Firmware
0009 – The serial number of the LR4
9999 – Can be written to in order to change the LR4’s Modbus address
All of the Modbus registers on the LR4 module are unsigned integers (16-bit
values / single register).
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