Store and Forward tags

What we call store&forward is the ability of the eWON to read a value from one protocol and to write this value on another protocol. It's like a "protocol converter" but with limitations.

For example, I want my S7-300 (with ethernet port) reads a temperature from a ModbusRTU device.
We can do that by placing an eWON (an eWON500 is enough) between the Siemens and the Modbus device.

In the ewon, you need to:

Define a "reading tag" on the Modbus device

Define a "writing tag" on the S7 device

Write a little BASIC script to assign the value read in the Tag to write

Here, you have several strategies to do this copy:

On timer

At a specified interval, you'll copy the value from one tag to the other.

In the Init section:

Ontimer 1,"goto TagsCopy"  
Tset 1,30

Timer section:

Ontimer 1,"goto TagsCopy"  
Tset 1,30

On change

nly when the read value will change, you'll copy the value from one tag to the other.

In the Init section:

Onchange "MbsTemperature","S7Temperature@ = MbsTemperature@"