Carrier CCU - 13.2 Communication Parameter Configuration; 13.3 ModBus Protocol Details

13.2 - Conguring the communication bus parameters (menu 7)
This menu gives access to all parameters used to dene the communication protocol and the 2-wire RS485 serial link parameters.
Access level No. Description Setting By default Display condition
2 700 Communication mode 1: MODBUS/JBUS 1
2 701 Communication speed
0: 4800 bauds
1: 9600 bauds
2: 19200 bauds
1
2 702 Parity
0: None
1: Even
2: Odd
0
2 703 Number of stop bits
1: stop bit
2: stop bits
1
2 704 Actual number format reversed
0: No
1: Yes
0
2 705 Slave number 1 to 255 1
2 706 Control type*
1: Local
2: Remote
1
* If the selected control type is local, the controller data can be accessed in read-only mode by the PLC; with remote selection, the controller data can be accessed in
read and write mode by the PLC.
13.3 - ModBus protocol
■ RS485 2-wire communication support
3-pin connector (J10)
Terminal 1: A or +
Terminal 2: B or –
Terminal 3: 0 V
Line termination resistor: Connected if COM1 is ON
Not connected if COM1 is OFF
External BUS polarisation.
■ Transmission mode
• Series, asynchronous, half duplex, one start bit, eight data bits,
• Parity congured by P702 (none, odd or even)
• Number of stop bits congured by P703 (1 stop bit or 2 stop bits)
• Communication speed congured by P701 (4800, 9600 or 19200)
• Slave no. on the bus congured by P705
■ Protocol
• ModBus (Gould Modicon)
• Compatible: JBUS (Merlin Gerin)
• RTU (GENERAL ELECTRIC protocol)
■ Codes of functions used
• 1 or 2: read n bits
• 3 or 4: Read multiple registers (16 bits) Maximum of 126 registers read
• 5: Write one bit
• 6: Write one register
• 8: Read diagnostic counter
• 11: Read event counter
• 15: Write n bits
• 16: Write multiple registers (16 bits)
■ Analogue value encoding
• Standard 32-bit IEEE format (2 registers).
• The byte order can be reversed with P704 (0:not reversed or 1:reversed)
NOTE: the register numbers correspond to the addresses coded on 16 bits.
■ Register denitions
• Function 3 or 4 is used for reading,
• Function 6 or 16 is used for writing.
13 - BUS FOR CONNECTION TO AN RS485 MODBUS CMS
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