Communication with 35 Modbus TCP/IP servers via AC500 PM591-2ETH PLC

Hello,

I have a requirement at site where I have to communicate with 35 Modbus TCP/IP Server devices (11 Modbus TCP to Modbus RTU/bacnet MSTP Gateways and 24 standalone Modbus TCP/IP servers.

I have gone through the below links which refer to a similar requirement and tried to implement the suggestions with reasonable success.

http://www402.abbext.com/AC500-Modbus...

http://www402.abbext.com/AC500-ETH-MO...

However, I am not able to achieve stable communication with all servers (24 standalone servers currently for testing purpose) over an extended period of time. I am using the usual method of connecting the DONE output of the preceding ETH_MOD_MAST block to the EN input of the succeeding block, to communicate with 24 different servers.

The 24 Instances of Modbus blocks are connected in a looped fashion in a single POU(PRG) and connected to a task of Priority=12 and Cycle Time=200ms.

Under Modbus Server settings,

Server Connections=0

Task TimeOut=1000ms

OMB Time=1000ms

(Currently Server protocol has been assigned to only one onboard ETH port.The two ETH ports have been set with different IPs)

With the above configuration, I am able to communicate with all 24 servers for some time , but after say 30 minutes, a random no of servers stop communicating (Error-8193) and then start communicating again after a finite time.

Hence, it would be of great help if anybody can suggest how to choose the corrrect codesys Task time,Task timeout, OMB time and also specify any tried and tested method of using the ETH_MOD_MAST blocks to achieve reliable and continous communication with a larger no of Modbus TCP/IP servers.

This issue as per my knowledge is concerned with Ethernet Sockets management.

Regards

Rahil