Process Image; Basic Structure - WAGO 750 Series Manual

6 Process Image

6.1 Basic Structure

After being started, the Linux fieldbus coupler automatically loads the internal
bus driver. It recognizes all the IO modules of the node that send or receive
data (data width/bit width > 0).
The node can consist of a mixed arrangement of a maximum of 64 analog and
digital I/O modules.
Note
The use of the WAGO module bus extension coupler module 750-628 and
end module 750-627 makes it possible to connect up to 750 modules to the
Linux fieldbus coupler 841-250.
Note
For the number of input and output bits or bytes of the individual IO modules
please refer to the corresponding description of the IO modules.
The coupler generates an internal local process image from the data width and
the type of I/O module as well as the position of the I/O modules in the Linux
fieldbus coupler node. This is divided into an input and an output area.
The data of the IO modules is separated for the local input and output process
image in the sequence of their position after the Linux fieldbus coupler in the
individual process image.
First, all the byte-oriented I/O modules are filed in the process image, then the
bit-oriented I/O modules. The bits of the digital modules are grouped into
bytes. Once the number of digital I/O's exceeds 8 bit, the coupler
automatically starts another byte.
Note
If a node is changed, this may result in a new process image structure. In this
case the process data addresses also change. In the event of adding modules,
the process data of all previous modules has to be taken into account.
WAGO-I/O-SYSTEM 750
Linux Fieldbus Coupler
Process Image • 127
Basic Structure