Mitsubishi Electric MelcoREMOTE, Installation And Operation Manual

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Page 48 of 52
16. Modbus Slave Register tables
All MelcoREMOTE I/Os are exposed as both Modbus Input (analogue input) registers and Modbus Holding
(analogue output) registers. The register numbers are the same for both register types.
Each I/O value is exposed as a 32-bit value, so two Modbus registers are used for each I/O value. The
lower of the two register numbers holds the most significant 16-bits of the I/O value.
Each I/O can be read in 9 different data formats; float32, uint32 (0dp, 1dp, 2dp and 3dp) and int32 (0dp,
1dp, 2dp and 3dp).
If an unsigned register (uint32) is being read then any negative value will be returned as value 0.
Outputs can have their values changed via a Modbus write commands to the Holding registers, using
function codes 6 and 16.
Here is an example Modbus RTU command to read configurable inputs 1 – 4 from Slave ID 1 as Input
registers in the data format uint32 (0dp):
01 04 13 DC 00 08 34 B2
where
01 is the Slave ID,
04 is the function code to read Input Registers,
13 DC is the start register (5084),
00 08 is the number of registers to read (8 registers as each I/O is comprised of two Modbus registers).
34 B2 is the 16-bit CRC.
An example reply from the MelcoREMOTE for the above command is:
01 04 10 00 00 00 17 00 00 26 6B 00 01 1F 17 00 01 1E C1 A5 E0
Where
01 is the Slave ID
04 is the function code to read Input Registers
10 is the number of data bytes following (16)
00 00 00 17 is the value of configurable input 1 (23)
00 00 26 6B is the value of configurable input 2 (9835)
00 01 1F 17 is the value of configurable input 3 (73495)
00 01 1E C1 is the value of configurable input 4 (73409)
A5 E0 is the 16-bit CRC
The following table gives the Modbus register numbers for each I/O type. The register numbers are all zero
based.