Automation Direct 405 PLC using MODBUS

Does anyone have experience connecting automation direct 405 series processors to Ignition using the MODBUS driver. I can connect to my devices and have all my tags set up. But for some reason randomly throughout the days my 405 processors will timeout from Ignition and will not reconnect. I have tried adjusted tag groups and adjusted timeout times on both ignition device setups and the Ecom modules for the 405 racks. But they still have this issue no matter what I try. Sometimes they come back online within 45 minutes, sometimes within 10 minutes. and sometimes they have lost communication for days and I have had to come up with other work arounds. If anyone has any insight as to why this may be I would greatly appreciate it. MODBUS seems to be the best and easiest way to access the tags I need for these devices so I would like to find a solution to this if possible. Thanks.

When Ignition looses comms can you still read/write using a modbus troubleshooting tool like modscan or modsim.

That im not sure of. Our IT department blocks alot of applications and the modbus tools are some of the applications that get blocked. I have other devices comminicating through modbus in ignition, and the 405 plcs are the only ones that ever disconnect and lose communication.

I don't get why modbus tools won't work, but modbus devices and software will?

You need to get IT to assist in getting these modbus tools working.

Next time it happens you can use a modbus tool. If the tool works reading and writing then you know its on the Ignition end. If the tool doesn't work you know it's on the PLC end or the network.

You could also use wireshark to see if the packets are getting kicked out by the firewall.

Can you ping the device when this happens? If not, can you run a ping trace and see where it gets held up?

I have looked at wireshark captures to try to see if i could see anything there. It seems like whenever they stop responding ignition is still requesting data and the devices are either sending out of sequence packets or not sending back the ack response at all. And i havent tried to ping the devices when they drop out. I will try that as well. It definitely seems like its specific to these PLC types. I also have several ti505 plc's communicating through modbus and they never have issues. Starting to wonder if its not a bug or limitation with these plc's causing the issues.

So another thing that I notices is we have a Master and a Backup gateway set up for redundancy. And while the master node stops talking to the PLC's, the backup still shows activity from the devices in question. Which seems to suggest that their might be an issues with the server our Master gateway is on that is causing them to disconnect and/or stop communicating.

Very likely, I would get in touch with your IT department and use that as proof it is their end holding it up