Why Does the A6 Driver Occasionally Fail to Respond to 485 Commands?

Let's first look at a description of this issue:

"But I have an issue that with a powered on but disabled drive the communication is stable, but when the drive is enabled between 1 in 10 or 1 in 20 messages I get a timeout on the communication. Resending the command works."

Analysis of the situation is as follows:

1. The drive can receive and process 485 commands normally when running, which rules out physical wiring errors and communication connection problems.
2. The motor and drive operate normally, indicating the product itself is not faulty.
3. The problem occurs after the servo is enabled but is absent when it is disabled. Therefore, the key factor is the "activation of motor enable."

This is a classic phenomenon in industrial communication known as "communication instability caused by interference." Simply put, after the drive is enabled, its internal power circuit switches on and off at high frequencies, generating strong electromagnetic noise (EMC). This noise can couple onto the RS485 communication lines, corrupting the communication signals and causing data packet damage or loss, which results in communication timeouts. If a USB-to-RS485 converter is being used, its weaker anti-interference capability makes it even more susceptible to this electromagnetic influence.

Solutions are as follows:

● Check Drive Grounding and Cable Shielding (This is the most likely cause): It is best to use twisted-pair shielded RS485 communication cable (similar to network cable).

● Use a Termination Resistor: Connect a termination resistor to the 485 output port of the last drive on the network.

● Connect Grounds: Connect the GND of the RS485 converter to the GND of the drive. This establishes a common reference potential for all RS485 devices and can effectively reduce common-mode interference.

● Reduce Communication Speed: Use the A6 drive's panel buttons or debugging software to appropriately lower the RS485 baud rate (C0A.09), for example, from the default 115200 down to 38400 or 9600. Lower speeds have higher tolerance to interference.

● Add Ferrite Cores: Place a ferrite core around the motor's power cables (U/V/W). Be careful not to thread the ground wire through the core.

In summary, the core of the issue is the electromagnetic interference introduced after the enable is activated. The highest priority checks should be grounding and cable shielding, followed by termination resistor configuration and GND connection.

Updated on: 28/02/2026