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:
TagsCopy: S7Temperature@ = MbsTemperature@ END
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@"