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In the head code of Modus RTU, Additional address is defaulted as 0x32, which can be changed by keys, the change
method is as shown in Table 4.2. Press the SW6+SW7 key for 3s and enter the setting mode.
Table 4.2 Modbus RTU additional address setting
NO.
·Press Up (SW5) or Down (SW8) until it displays “485.”.
·In “485.” Menu, press Select key (SW7) and confirm to enter additional address
setting mode.
·After set, press Eject/Switch (SW6) key to exit.
·Press SW7 so that additional address becomes editable, flashing in 1Hz.
1
·In menu, press Select key (SW7) so that the default Additional address flashes and
becomes editable.
·Press Eject/Switch key (SW6) to switch flashing, and change editable area.
·Press Up (SW5) or Down (SW8) to change the number of additional address.
Prompt
●
To reset additional address into factory default value, same operation as reset default IP address, please
refer to Table 3.2 Set IP address No.6.
When using Modbus RTU, firstly need to configure it, please refer to Table 4.3 for the configuration parameter.
Table 4.3 Modbus RTU Parameter Matching
Modbus RTU Configuration Name
Configuration Data
Remark
Additional address
0x32
Default value
Baud rate
9600 bps
——
Parity No
Parity ——
Data bit
8bit
——
Stop bit
1bit
——
4.1.2 Modbus TCP Code Composition
On TCP/IP, one special message header is used to identify the Modbus application Data unit, which is called MBAP
message header.
Modbus TCP/IP ADU
PDU
Data
Function code
MBAP message header
Figure 4.3 Modbus TCP/IP Frame Data
While Modbus TCP ADU = 25 MBAP (7 bytes) = 260bytes.
The length of MBAP message header is 7 bytes:
①
Transaction identifier [2 bytes]: pairing for transaction processing. In response, Modbus adapter will copy the requested
transaction identifier.
4 Air Conditioner Monitoring