Description for Modbus protocol interface
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Part 7: Description for Modbus protocol interface
7.1. Device connection
Unit’s electric control cabinet provides the RS485 communication interface convenient for the user's
monitoring the operation condition of the unit and system integrating. As long as the users follow the standard
MODBUS protocol and comply with the protocol point table provided by us, they can monitor the unit easily.
7.1.1. Communication Cable
1.
The A and B of the XTB2 terminal in 1# unit’s electrical cabinet are the communication interfaces between the
unit and the computer. There must be a RS232/485 active or passive converter in the middle of them. The
communication line has polarity. A is connected to converter A (or +). B is connected to converter B (or-). Do not
connect them in a wrong way for fear of the occurrence of the Fault.
2
Communication distance shall be within 100 meters by using the 2×0.75mm
2
shielded twisted pair;
Communication distance shall be within 100-500 meters by using the 2×1.0mm
2
shielded twisted pair;
7.1.2. Connection Mode
Schematic Diagram of Connection Mode
7.2. Modbus Protocol
Basic Description of the Protocol
1 MODBUS RTU Protocol; CRC Check;
2 9600bps; 1-Bit Start Bit; 1-Bit Stop Bit; No Check Bit; 8-Bit Data Bit;
3
Definition of Temperature Data: 16-Bit Signed Digital (-32768 ~ + 32767); Actual Temperature = Temperature
Data/10; Unit:°C;
4 Buffer Size: 256 Bytes
System Content/Chiller Setpoint
HMI ON/OFF Command
3, 6, 16
0
0-Invalid; 1-On; 2-Off
Setting Range Shall Be the
Same as Unit’s Set Value
HMI mode command
3, 6, 16
1
0-refrigeration; 1-heating;
2-heat recovery; 8-water
pump cycle
Setting Range Shall Be the
Same as Unit’s Set Value
Set value for refrigeration
backwater temperature
3, 6, 16
2
°C, ×10
Setting Range Shall Be the
Same as Unit’s Set Value
Set value for heating
backwater temperature
3, 6, 16
3
°C, ×10
Setting Range Shall Be the
Same as Unit’s Set Value
Set value for refrigeration
outflow water temperature
3, 6, 16
4
°C, ×10
Setting Range Shall Be the
Same as Unit’s Set Value
Set value for heating outflow
water temperature
3, 6, 16
5
°C, ×10
Setting Range Shall Be the
Same as Unit’s Set Value
Cooke Industries - Phone: +64 9 579 2185 Email: [email protected] Web: www.cookeindustries.co.nz