Ping Command in CompactLogix/ControlLogix PLC

mahone

Member
Join Date
Apr 2014
Location
Singapore
Posts
62
hi all,

how to implement Ping command in CompactLogix PLC so that i can
check the com link between the plc and a computer it's connected to?

thanks
 
I may well be mistaken, but I believe the ping command will have to come from the PC to the PLC, not the other way around.

Bubba.
 
I'm not aware of any PLC that has a Ping command native.

My understanding is that you can send TCP or UDP packets with the MSG command. These allow you to implement most protocols, but you would pretty much need to be able to send raw Ethernet (layer 2) packets to be able to do Ping or other ICMP commands.
 
Most PLC doesn't do ping. What you can do is a watchdog or heartbeat.

Depending on where you want the alarm to be fired off you would have the other side send a changing sequence and check for for that variation. If it stops, fire off the alarm.
 
You almost certainly don't want a PING command. PING doesn't tell you anything about the status or type of device on the network.

You probably want a watchdog function. I usually do this by having the HMI computer write the /Seconds value from the PC clock to the PLC. As long as the tag it is writing to is changing, I know that the PC is connected and that the HMI program is executing.

Another method I have used with PanelView and computers running RSLinx is to send a MSG instruction with the CIP object to read part of the Identity Object. When you get a reply to such a message, you know that the computer is connected and that RSLinx is running.
 
You almost certainly don't want a PING command. PING doesn't tell you anything about the status or type of device on the network.

You probably want a watchdog function. I usually do this by having the HMI computer write the /Seconds value from the PC clock to the PLC. As long as the tag it is writing to is changing, I know that the PC is connected and that the HMI program is executing.

Another method I have used with PanelView and computers running RSLinx is to send a MSG instruction with the CIP object to read part of the Identity Object. When you get a reply to such a message, you know that the computer is connected and that RSLinx is running.
I want to check if FTLinx is running on a PC. @Ken Is this possible using the method mentioned. If so, can you give some more details on reading the identity object please?
 
We build watch dog heart beats into most of our SCADA systems.
Every 250 ms we increment a tag in the PLC from the SCADA system.
.
This gives you dynamic live data about the system connection, unlike a ping that is only a low level check.
.
We do this in:
Wonderware, Ignition, Citect, RsView, Win CC, LabView
 
We build watch dog heart beats into most of our SCADA systems.
Every 250 ms we increment a tag in the PLC from the SCADA system.
.
This gives you dynamic live data about the system connection, unlike a ping that is only a low level check.
.
We do this in:
Wonderware, Ignition, Citect, RsView, Win CC, LabView
 
Ping will merely tell you that the IP address you pinged is connected to the network. It may even be another PLC, IO, HMI, Server, you name it... but it won't be Linx.
I am aware of this. The only reason I replied in this thread was because I wanted more information on Ken’s post regarding the identity object.
 
You should be able to read a packet of data and write a packet of data to and from the device using GSV commands but not the simplest and may take a bit of time with wire shark, best way is to re/write a Tag to/from Scada and verify as a watchdog.

Mmaybe a better question to ask is why do you need to know the machine is alive or dead? Does the PLC need to know the PC is present?
 
Mmaybe a better question to ask is why do you need to know the machine is alive or dead? Does the PLC need to know the PC is present?[/QUOTE]

Sometimes the PC collects data from other sources the PLC uses for interlocks, if the PC stops communicating we shut down some devices.
 
I would imagine it might be possible to construct one with open sockets wouldn't it? Not that I would know how, but I thought Open Sockets opened all possibilities...
 

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