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6.2. Manual Mode
When the switch on the front panel is set to 'Manual' the MelCOMMS MINI will not perform any control of the indoor
units. The Fault Relay and High Temp Relay will still operate in Manual mode.
6.3. Rotation Test Mode
MelCOMMS MINI can be put into rotation test mode by powering up the unit with a wire link placed across inputs IN01,
IN02 and IN03 (see section 5.4 – Configuration).
In this mode the rotation period for automatic control will be set to 1 minute. If using custom settings the high
temperature alarm will be disabled.
6.4. Modbus Slave Test Mode
MelCOMMS MINI can be put into Modbus slave test mode by powering the unit up with the 8 DIP switches 1-1 to 1-8
all in the OFF position. In this mode the MelCOMMS MINI unit will not attempt to communicate with any MelcoBEMS
MINI (A1M) devices, the RS-485 port will instead be used to provide Modbus RTU Slave functionality.
In this mode the MelCOMMS MINI will have the following fixed communications settings:
-
Slave ID
-
Baud rate
-
Data bits
-
Parity
6.4.1. Modbus registers
Using a Modbus Master PC utility the current state of all MelCOMMS inputs can be monitored and the relay outputs
can be temporarily switched for testing purposes.
The tables below show the Modbus registers supported:
Register Name
Fault Relay Output
High Temp Relay Output
Coil Status Registers can be read using function code 1, they can be written using either function code 5 or 15.
Function code 5 is used when writing to a single Coil register, function code 15 is used for writing to multiple coil
registers in the same command.
1
9600
8
None
Coil Status Registers (Digital Outputs)
Address
0
1
Modicon
Address
00001
0 = Relay OFF (de-energised)
1 = Relay ON (energised)
00002
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