Micrologix1400 MSG Error: Local Communication Channel is Shutdown

[jolson148]

I am trying to communicate with a Moxa Ethernet to serial converter that is going out to a Modbus device. I have my Moxa set up with an IP of 192.168.1.98 port 4001. I have my MSG instruction set up as
1(integral, Modbus TCP)
03 Read holding registers
trying to poll 1 element @16bit
I have a valid RI11:0 entered
IP of 192.168.1.98 and port 4001

I keep getting a fault code ff and the description is local communication channel is shutdown. I have Modbus tcp enabled under channel 1 configuration and have the channel 1 Modbus tab at the top.

What am I missing or doing wrong?

Thanks

 

[Ken Roach]

Welcome to the PLCTalk Forum community !

Why are you using TCP Port 4001 instead of the standard Modbus/TCP Port 502 ?

Also, be sure you have power cycled at least once after Enabling Modbus/TCP on Channel 1. That function requires a hard reboot at least once after it is enabled, and the FFh error code is characteristic of that issue.

 

[jolson148]

Thanks the power cycle was my issue. The 4001 port is what the MOXA comes with in its generic config.

 

[Ken Roach]

Glad to hear you got it sorted out, and I appreciate the response post.

I recommend that you configure the Moxa and the MicroLogix to use the ordinary "well known" TCP Port 502 for Modbus/TCP.

Port 4001 is a "registered port" with unofficial uses, none of which are relevant to Moxa or Modbus/TCP (like the old Microsoft Ants game !). If somebody had to come analyze your network in the future they would start looking for Port 502.