I prefer to use MOdbus to gather information related to remote IO in RTU and send them using in IEC 101 to the controlled station ,the problems rasies here :

1)modbus use req/resp structure which makes me to retrieve all or some digital and analouge information in polling(using addresses) instead of just sending me Change of state or measured valuse,Sending all informmation everytime i poll remote IO takes lots of my bandwith and also times,i just need the changes of each valuse not all in every request i send to remote IO.

2)evey changes has a timetag in RTU how can i transmite time tag in modbus?

Best regards
Majid

 

In Modbus a master sends a command while the slave sends a response. In Modbus you can send a command to retreive data and time in the same response as long as all the data is in successive register (bytes). The problem with modbus is you need to ask for data for a slave to respond.
If you need what they call a "Consumer/producer" protocol you have to use the CAN bases protocols (CANOpen, Devicenet, Controlnet, ...)

 

Do not poll the I/O from the RTU, have the RTU send the info on change of state. IE Always write info, never read if you want to do this between two modicon plcs. If the RTU is not a processor, just I/O then you are stuck polling all the data.