72 • Feldbus Coupler/Controller

Fieldbus Controller 750-806

3.2.4 Process Image

After switching on, the Controller recognizes all I/O modules plugged into the node which supply or wait for data (data width/bit width > 0). In nodes, analog and digital I/O modules can be mixed.

The Controller produces an internal 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 node. It is divided into an input and an output data area.

The data of the digital I/O modules is bit orientated, i.e. the data exchange is made bit for bit. The analog I/O modules are all byte orientated I/O modules, i.e. those where the data exchange is made byte for byte. These I/O modules include, for example, the counter modules, I/O modules for angle and path measurement as well as the communication modules.

Note

For the number of input and output bits or bytes of the individually activated on I/O modules please refer to the corresponding I/O module description.

The data of the I/O modules is separated from the local input and output process image in the sequence of their position after the controller in the individual process image.

In the respective I/O area, first of all analog modules are mapped, then all digital modules, even if the order of the connected analog and digital modules does not comply with this order. The digital channels are grouped, each of these groups having a data width of 1 byte. Should the number of digital I/Os exceed 8 bits, the Controller automatically starts another byte.

Note

A process image restructuring may result if a node is changed or extended. In this case, the process data addresses also change in comparison with earlier ones. In the event of adding modules, take the process data of all previous modules into account.

The process image for the physical bus module data is identical with that of the WAGO DeviceNet fieldbus Coupler.

With the Controller, the data of the PFC variables are filled into the process image, separated according to input and output data.

WAGO-I/O-SYSTEM 750

DeviceNet