Need a bidirectional unit that will allow a modbus input but has a redundant (ie: dual) modbus/tcp ethernet output.

Im using sixnet ethertrak et-gt-st-3 which has a serial port and two ethernet ports. The serial port reads modbus RTU, then sends modbus TCP through ethernet port to the pks experion software where this application is running a modbus controller. Everything works fine. But the problem is when i lose serial communication, i cant find a way to be aware of that. What i mean is that the sixnet ethertrak keeps sending the last values he has in storage. So in the pks experion everything seems to work fine (the values are just frozen). There must be a way that the sixnet ethertrak tells that serial communication is loss

pd: I've already tried the sixnet watchdog, but i need something that tells that the serial channel is down.

Thanks

 

As I understand, it no communication failure detection in ethertrak unit. In such cases you can do following:

1. generate a digital bit in your primary device where your Modbus slave and read it with ethertrak in every cycle.

2. Read this bit in ethtrak and keep it in "1" with timeout about 3 times more than the reading cycle time. After timeout put your bit to "0".

3. This bit you can use as a communication failure bit and you can even stop Modbus/TCP communication or detect com failure in your Experion Scada.

Regards, Peter

 

This solution is not exactly what i am looking for. Ok, i could generate this status bit (it could be a heartbeat)and then in my experion software i can monitor if this bit stops changing states and trigger an alarm that tells me that i lost serial communication, perfect. But, my software experion will continue to read the last values registered by the sixnet gateway, and this is exactly what i want to avoid. I want to find a way to stop sending these incorrect values to my software experion. Maybe there must be a way that my controller in the software experion can read from the modbus terminal where the gateway is transparent. I know that the sixnet has a pasthru mode, where i can pass commnands between serial port and ethernet port. That way, i could control directly my modbus terminal from my software experion. The problem is that this passthru mode in the sixnet is just available when you are working with sixnet protocol and not with RTU modbus protocol. If someone has an idea, please help me. I have tried with the sixnet I/O transfers with no good results.

thanks

 

You can easily disable the controller or channel that has failed with a simple server script that monitors that watchdog. Doing this will then tell the EPKS server that all of the data is no good and your graphics will show greyed out values that will be reported as not valid to other applications like OPC.

Do you have the Diagnostic Address set on the Controller definition? Also, with Modbus/TCP to serial converters you may want to speed up the diagnostic scan time on the channel and turn the fail and warn levels down. This should make the controller loss function work as designed. See the Quickbuilder controller help for assistance.

Art