70
Function Description
WAGO-I/O-SYSTEM 750
750-806 Fieldbus Controller DeviceNet
TM
Manual
Version 2.0.0
7.2
Process Data Architecture
7.2.1
Basic Structure
After switching on, the fieldbus controller identifies all I/O modules connected
with the node that send or receive data (data width/bit width > 0).
In a node can consist of a mixed arrangement of analog input/analog output
modules and digital input/digital output modules and special modules.
Additional Information
For the number of input and output bits or bytes of the individual I/O modules,
refer to the corresponding description of the I/O modules.
The fieldbus controller creates an internal local process image on the basis of the
data width, the type of I/O module and the position of the module in the node.
This process image is broken down into an input and an output data range.
The data of the digital I/O modules is bit-oriented; i.e., digital data is sent bit by
bit. Analog I/O modules represent the group of byte-oriented modules – data is
sent byte by byte.
Counter modules, DALI, MP bus, EnOcean and communication modules, for
example, are included in this group of modules.
For both, the local input and output process image, the I/O module data is stored
in the corresponding process image depending on the order in which the modules
are connected to the fieldbus controller.
For both the local input and the output process image, the I/O module data is
stored in the corresponding process image according to the order in which the
modules are connected to the controller.
First, all the byte-oriented (analog) IO modules are filed in the process image,
then the bit-oriented (digital) IO modules. The bits of the digital modules are
grouped into bytes. If the amount of digital information exceeds 8 bits, the
controller automatically starts with a new byte.
Hardware changes can result in changes of the process image!
If the hardware configuration is changed by adding, changing or removing of I/O
modules with a data width > 0 bit, this result in a new process image structure.
The process data addresses would then change. If adding I/O modules, the process
data of all previous I/O modules has to be taken into account.
