Micrologix 1100 & 1400 freezes with radio

[IamJon 0]

There is an undocumented problem with MLX 1100 and 1400 when used with a master telemetry unit radio. The radio dumps too much data into it that it freezes up and errors. This is not the case with the 1200 and 1500 because they use a separate ethernet card. Has anyone heard of this and come up with a solution while still using the MLX and radio?

[pcmccartney1 141]

I've had repeated problems with ML1100 Ethernet port lockups. RA simply says to upgrade the firmware to the lastest and greatest and that the problem should resolve itself. That's all fine and dandy, but I've gone from v1 all the way v9 and the problem still exists. In my case, I'm attached to a Digi WAN/WAP with a cellular SIM card installed and a VPN tunnel. Love to hear a possible solution.

[paulengr 44]

This is a common problem with practically any Ethernet system. The NIC card is fairly "dumb" and just receives/validates packets. It does not actually execute the code to interpret the results. If you exceed a certain load (in packets per second), the device will lock up. This is also certainly a problem with the 20-COMM-E boards on Powerflex drives (they specify a pretty low packets/second rate). You need a way to throttle the packet flow rate, either externally or internally. Most managed Ethernet switches have this capability. I know for a fact that you can do it with a Cisco switch, a Hirschmann switch, and a Sixnet switch. I don't know about any others simply because I don't have experience with them. This is also a routine problem with a lot of other devices, including PC-type devices. The only difference is that those devices usually have a lot more processing power available. For PC's using the iSCSI protocol (the fastest growing protocol for server/SAN connections), and NIC cards now in the 10 Gbps speed, this is becoming a serious problem for PC's. The solution in the PC world (aside from packet throttling) is to use TOE (TCP/IP Offload Engine) NIC cards which have built-in processors that handle the basic TCP/IP protocols, offloading some of the work from the main CPU. This is effectively how the ControlLogix works (it has a separate I/O processor) as well. No solution though for an ML1100/1400 except to use a managed switch and throttle the packet stream. I don't have any idea what the maximum rate is but I probably wouldn't try pushing much past 1000-2000 packets/second.

[Ken Roach 194]

I have seen both reliable and unreliable systems that use MicroLogix 1100 and 1400 with IP radios. In general I find the MicroLogix embedded Ethernet ports to be much more capable than the 1761-NET-ENI used with MicroLogix 1000/1200/1500 controllers (more TCP connections, more packets/second), so my expectation is opposite from your experience. Can you describe more about your system ? There are likely configuration, programming, or troubleshooting steps you can take that will improve the system's communications reliability.

[IamJon 0]

It isn't my project... I don't have any details. All I know is it's a 2.4 MHz radio sending to a MLx 1100 or 1400.

[Ken Roach 194]

I really can't suggest anything based on such thin information. If the people responsible for the system can provide some information, maybe forum members could help. With regard to pmccartney1's description of a Digi cellular access point, I'd recommend opening a separate thread and including more details about your system. I'm interested to know if it's accessible from the Internet or only via VPN. I've solved a lot of VPN connectivity problems, but never one involving a cellular bridge, and it sounds like a neat challenge.

[IamJon 0]

^Sorry for the lack of info. It was just intended to be a general question. They've already switched out the Mlx's for CompactLx, and are getting new radios. This was just something a co-worker brought to my attention, so I figured I'd see if anyone else has experience with it.