Technical data

WAGO-I/O-SYSTEM 750 Function Description 39
750-652 Serial Interface RS-232 / RS-485
Manual
Version 1.3.0
Figure 7: Internal Structure
If two I/O modules are connected together in this mode, each I/O module
transmits the data bytes of the process output image cyclically to the I/O module
on the opposite side. Received data bytes of the process output image on the
opposite side are again represented as data bytes in the process image of the local
I/O module. The sequence of data bytes remains unchanged during transmission.
The cycle, in which process data is exchanged between I/O modules, is event
driven. The I/O module only starts the next transmission after assessing the
transmission of the opposite side as error-free. The I/O module then also begins a
new transmission if no error-free transmission has been received from the
opposite side for a period of at least 200 ms. This ensures that data exchange is
automatically resumed in the event of simultaneous operation or temporary
disturbance of the transmission.
The I/O module monitors the process data received from the opposite side for
actuality. If no error-free transmission was received from the opposite side for a
period of at least 200 ms, the I/O module sets all data bytes of the process image
(input) to zero.