A6 Servo Motor RS-485 Communication Guide

We have received feedback from customers who have questions about using Modbus RTU over RS-485 to control A6 series servo motors. To help users better understand and use the RS-485 communication features of the A6 series, this guide provides detailed wiring instructions and practical command examples.

Important: Saving Parameters Written via RS-485 To save parameters written via RS-485 to non-volatile memory, you must send the following save command. Otherwise, all modified parameters will revert to factory defaults when the drive loses power.

01 06 0A 05 00 01 CRC CRC

1. Initial Connection and Communication Setup

Required Preparations

• An A6-RS series servo drive with motor and power cables connected
• An RJ45 Ethernet cable
• An RS-485-to-USB adapter cable (If you are unsure which one to choose, we recommend our product: USB to RS-422/RS-485 Serial Port Converter Adapter Cable)
• Serial communication software or a controller capable of sending Modbus RTU commands

Wiring

Refer to the RS-485 interface pin definitions in the A6-RS series manual:

Compare with the pinout of the RJ45 Ethernet cable:

As shown in the diagrams, connect wires 4, 5, and 8 to the RS-485-to-USB adapter cable.

For the RJ45 Ethernet cable:

• Leave the RJ45 connector on one end intact for plugging into the drive's CN3 port.
• Cut off the RJ45 connector on the other end.
• Strip wires 4, 5, and 8 (blue, blue-white, and brown wires) and connect them as follows:

After wiring, plug the RJ45 connector into the drive's CN3 port and connect the USB adapter to your PC. Power on the drive and open the serial communication software to establish communication. If communication fails, refer to this troubleshooting article.

2. Operation Modes

2.1 Speed Control Mode

As shown in the examples above, parameter register addresses in the A6 series do not require complex conversions. For instance, to set C00.00 to 1, the register address in the RS-485 command is simply 0000. Similarly, setting C03.20 to 3 uses register address 0320.

The only conversion required is for the write value. All parameter values in the manual are listed in decimal format, but RS-485 commands require hexadecimal values.

Important: Data Types and Register Sizes

In Chapter 8 of the manual, the parameter table includes a "Data Type" column. Note that data types vary across parameters:

Pay close attention to the data type:

U16 — 16-bit unsigned parameter (use write command 0x06):

Example: 01 06 00 00 00 01 CRC CRC (sets C00.00 to 1)

U32 — 32-bit unsigned parameter (use write command 0x10):

Example: 01 10 12 0A 00 02 04 00 64 00 00 CRC CRC (sets C12.0A to 100)

I16 vs. U16: The difference between I16 and U16 is that I16 represents signed 16-bit values (supporting negative numbers), while U16 represents unsigned 16-bit values. If a parameter can accept negative values, its data type is I16. Typically, speed-related parameters may have negative values, where negative and positive values indicate opposite motor rotation directions.

2.2 Multi-Speed Operation

2.3 Absolute Position Movement — 5000 Pulses (Default: 10000 Pulses/Rev, C00.02=10000)

2.4 Multi-Position Operation Under Absolute Positioning (First Segment: 3000 Pulses; Second Segment: 8000 Pulses)

Note: In absolute positioning mode:

• The first segment moves to position 3000 pulses (relative to origin 0).
• The second segment moves to position 8000 pulses (relative to origin 0).

To operate in relative position mode instead, set C11.01=1. In this mode, the second movement starts from the 3000-pulse position and moves an additional 8000 pulses forward.

3. Common Commands

Note on torque readings: The read value unit is 0.1%. For example, a reading of 1000 corresponds to 100.0%, which equals 1× the motor's rated torque.

Note on temperature readings: The read value unit is 0.1 °C.