12-1
Data subject to change without notice 7/07. © 2007 GE Drives
The serial interface supports operation, configuration and monitoring of drive functions through an EIA/RS485 connec-
tion. The serial interface is based on Modbus RTU protocol. This protocol allows the drive to function as an RTU slave
on an industrial network.
12.1 Transmission Specification
Item Specification
Physical level EIA/RS485
Transmission distance 500 m max.
Number of nodes 32 total
Transmission speed 19200, 9600, 4800, 2400 [bits/s]
Transmission mode Half duplex
Transmission protocol Modbus RTU
Character code Binary
Character length 8 bits
Error check CRC
12.2 Connection
Connection method
Use shielded wire and connect to the control terminals (DX-, DX+ and SD). A termination resistor should be added
between the data lines on the each end of the network. The value of the termination resistor depends on the character-
istic impedance of the cable. A common value for termination resistors is 120 ohms.
Control terminals
Terminal
marking Terminal name Function description
DX+ RS485 communication data (+) Input/output terminals for RS485
DX- RS485 communication data (–) communication.
SD Cable shield Electrically floating
12.3 Serial Interface Configuration
Drive function codes H30 to H39 are used to configure the serial interface parameters, such as device address, baud
rate and error response.
12.4 Modbus RTU Functions
The following RTU functions are supported. The maximum number of consecutive parameters for function 03 and 16
messages is 16.
Code Description
03 Read Holding Registers (16 registers maximum)
06 Preset Single Register
16 Preset Multiple Registers (16 registers maximum)
12. RS485 Modbus RTU Serial Communications
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