RSView32 - MicroLogix 1400

We changed a switch that is between two Control panels and a PC. Now the RSView32 is saying " Channel Error - Application Layer Timeout"

I see that whenever I change the Switch, the listening port (tested using netstat -a) changes.

I tested using ping and tracert and both commands say that connection is successful.

Appreciate any help. Many Thanks.

With power on, try switching the cables around on the Ethernet switch to random ports. I've had this resolve weird communication failures.

thank you. I tried changing ports and changing switches but the same problems persist. Port number is randomly assigned when the PC is restarted, so that shouldn't be a problem.

sometimes the error is "illegal command or prompt" - Rockwell website says the channel is wrongly named as PLC when an SLC is used, but I checked this and it is fine. I am using SLC 5/03; so its SLC-5 enhanced channel.

Sometimes the error is "alarm detector has been notified of communication error"

sometimes the error is "main/enable failed"

Was your original switch a managed switch? What model of switch was it?

Dont know; it went missing after renovation of control room and I am using an unmanaged switch now....do you recommend a managed switch? what are the issues here? I am not sure; kindly help.

If the original switch was a managed switch, it might have been doing some routing or had a VLAN configuration... but if you don't have the configuration of the original managed switch, you'll never get the settings back, unless you know the people who originally configured your network.

Try only connecting the RSView32 and ML1400 to the switch, without any other connections to the switch.

PS: check the Windows network settings on the RSView32 PC. Is it static IP, or DHCP? Also the PLC, is it static IP, or DHCP? And what are the IP addresses?

thank you. I will contact them, not sure if they still have a record. Also, will buy a managed switch and check the Windows configurations.

the PLC are static; we have the IP addresses written down:
198.168.1.2
198.168.1.3

The ports on PC that are listening are dynamic (i think).

PS: I removed the switch and connected each PLC directly to PC; there still was a problem....may be there is an interlock to start both at the same time.

Also, will buy a managed switch

Click to expand...

Keep in mind, it might be an issue that a managed switch was installed, but not 100% guaranteed.

Can you check the RSView32 configuration, to make sure the correct IP addresses are used for the PLCs? Make sure the computer is on the 192.168.1.x network. If not, and the computer is set for DHCP, try setting a static IP to an unused IP on the network.

PS: It is possible that a managed switch has a DHCP server feature, and it's possible that the switch was assigning the IP address to the computer.

sigmadelta said:

PS: It is possible that a managed switch has a DHCP server feature, and it's possible that the switch was assigning the IP address to the computer.

Click to expand...

I think so after you said,

PC is on same network and RCView32 are using the same IP; I checked the nodes and channels.

Thanks a lot for your help; after you said, I checked online and found the following (taken from one of the manuals):

Unmanaged Switches
• NOT recommended for FactoryTalk (RSView SE) applications!
• Not configurable, but route data more intelligently than hubs. They typically do not have large buffers and there is a chance of collisions, errors, dropped packets, packet timeouts.
• Are not assigned IP or Mac addresses (they are “transparent”)
• NIC cards used with unmanaged switches should be set according to the switch manufacturer’s recommendation


Managed Switches
• Highest cost, highest functionality. Managed switches (commercial or industrial grade) are recommended for FactoryTalk (RSView SE) applications.
• They are configurable with extra functionality like traffic optimization, fault tolerance mechanisms, alarms, monitoring, packet prioritizing, diagnostics, etc.
• Are assigned IP addresses (they are seen as a node or station on the network)
• NIC cards used with managed switches should be set to the maximum network speed and Full Duplex (e.g., 100MB/Full Duplex).

Bought a managed switch. Finally realized that the Switch is NOT the issue. The Battery on the SLC died and the RAM lost the Program. Have to reload the program and also change the battery.

This explain why ping and tracert is successfully connecting to SLC, but communication is failing - SLC program is lost and needs to be reloaded.

What an unfortunate coincidence! Two problems occurred at once, but it looked like the switch was the problem.