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12. Modbus
register
tables
Some BMS controllers can only read Modbus Holding Registers, so the MelcoRETAIL MINI also exposes all Discrete,
Coil and Input Registers as Holding Registers. The Discrete Input registers and Input registers are not writable so their
equivalent Holding Register is read only and marked [
READ ONLY
].
Some BMS controllers may not be able to read signed register values (i.e. values which can be negative in value), so
the MelcoRETAIL MINI also exposes an unsigned version of those registers (these registers will not return a negative
value).
12.1.
Holding registers
Holding Registers are read using function code 03 and written to using either function code 06 or 16. Function code 06
is used when writing to a single holding register, function code 16 is used for writing to multiple holding registers in the
same command.
Holding Registers (Analogue Outputs)
Register Name
Address
Modicon
Address
Details
Drive Mode
0
40001
1 = Heating
2 = Humidity reduction
3 = Cooling
7 = Ventilation, clean air operation
8 = Auto Operation
9 = i-see heating operation
*
10 = i-see humidity reduction
*
11 = i-see cooling
*
*
indicates a read only value, writing this value will
have no effect
Temperature Setpoint
1
40002
Temperature value in °C multiplied by 10.
e.g. value 200 = 20°C
Fan Speed
2
40003
0 = Auto
2 = Quiet
3 = Weak
5 = Strong
6 = Very strong (SH i)
Air Direction
3
40004
0 = Auto
1 = Position 1
2 = Position 2
3 = Position 3
4 = Position 4
5 = Position 5
7 = Swing
Modbus Slave ID
4
40005
Values 1 – 247 valid
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