12.4 Exceptions and Troubleshooting

12.4.1 Common Error Causes

Although by no means exhaustive, Table 3 provides possible causes behind some of the most common errors experienced when using the Modbus TCP/IP interface.

Table 3: Troubleshooting Reference

Problem

Register addressing is off by 1

Modbus TCP/IP client cannot establish communication with the ETH-100

Drive does not respond to network commands / frequency command

ILLEGAL FUNCTION exception (Modbus exception code 01)

ILLEGAL DATA ADDRESS exception (Modbus exception code 02)

ILLEGAL DATA VALUE exception (Modbus exception code 03)

NEGATIVE ACKNOWLEDGE exception (Modbus exception code 07)

GATEWAY PATH UNAVAILABLE exception (Modbus exception code 0A)

GATEWAY TARGET DEVICE FAILED TO RESPOND exception (Modbus exception code 0B)

Possible Cause

Refer to Section 12.3.2 for direct mapping

•Ensure at least one of the connected drives is powered on

•Check that the drive and Ethernet communication cables are fully seated into their respective communication ports

•Check the Ethernet communication parameters (IP address, etc.)

•Check drive’s frequency mode and command mode selection parameters

•Where applicable, confirm the values of bits #14 and #15 of communication command word

•Confirm that the communication frequency command value is between lower limit and upper limit frequencies

The indicated Modbus function is not supported: refer to section 12.2 for a list of supported functions

The targeted drive register (or one in a group of targeted registers) does not exist: check the drive’s supported register list

The value written was rejected by the drive as invalid: check the value and drive setting range

•An attempt was made to write to a drive register while the drive was running that does not accept writes while the drive is running

•An attempt was made to write to a read-only register

•Confirm that the drive communication cable is fully seated into the drive’s and ETH-100’s communication ports

•Confirm that the drive communication cable is not routed near the drive’s input power or motor wiring or any other electrical noise-producing cables or equipment

Unit Identifier (UI) was invalid: UI must be 1 ∼ 3

The targeted drive is not online or failed to respond:

•Confirm that the targeted drive is powered-on

•Confirm that the drive communication cable is fully seated into the drive’s and ETH-100’s communication ports

•Confirm that the drive communication cable is not routed near the drive’s input power or motor wiring or any other electrical noise-producing cables or equipment

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