Data Exchange Operating Mode Application Example - WAGO 750-652 Manual

58 Commissioning
8.3.7

Data Exchange Operating Mode Application Example

In the "Data Exchange" operating mode, the I/O module monitors process data
exchange with the partner module. If the connection is interrupted for 200 ms or
more, it generates a diagnosis in the status byte. This monitoring only takes into
account if there is a connection between the I/O modules. As the user, you may
want to check if the application that accesses the fieldbus node of the opposite
side as a PLC application or via fieldbus has received the information sent.
You can easily implement this monitoring by reserving three bits in the data part
of the process image for transmission of status information. Use bits 0, 1 and 2 of
the first data byte, for example.
Use bit 0 as the "ON" signal on both sides.
1. Describe bit 0 in the process image (output) permanently with status 1.
2. Check if the "ON" signal is displayed correctly in the process image (input).
No connection if the status is "0"
If the status is 0, there is no connection with the opposite side and all data bytes of
the process image (input) of the I/O module are invalid.
Use bit 1 as the "toggle" bit to send data to the opposite side.
3. Invert the sent "toggle" bit if you want to send new data.
If you have already sent data, you can only send new data if the opposite has
acknowledged receipt.
Use bit 2 as the "acknowledge" bit on both sides to signal data receipt to the
respective opposite side.
4. Always invert the sent "acknowledge" bit if the received "toggle" bit has
changed.
WAGO-I/O-SYSTEM 750
750-652 Serial Interface RS-232 / RS-485
Manual
Version 1.4.0