Process Image ï 127Basic StructureWAGO-I/O-SYSTEM 750Linux Fieldbus Coupler6 Process Image6.1 Basic StructureAfter being started, the Linux fieldbus coupler automatically loads the internalbus driver. It recognizes all the IO modules of the node that send or receivedata (data width/bit width > 0).The node can consist of a mixed arrangement of a maximum of 64 analog anddigital I/O modules.NoteThe use of the WAGO module bus extension coupler module 750-628 andend module 750-627 makes it possible to connect up to 750 modules to theLinux fieldbus coupler 841-250.NoteFor the number of input and output bits or bytes of the individual IO modulesplease refer to the corresponding description of the IO modules.The coupler generates an internal local process image from the data width andthe type of I/O module as well as the position of the I/O modules in the Linuxfieldbus 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 processimage in the sequence of their position after the Linux fieldbus coupler in theindividual process image.First, all the byte-oriented I/O modules are filed in the process image, then thebit-oriented I/O modules. The bits of the digital modules are grouped intobytes. Once the number of digital I/Oís exceeds 8 bit, the couplerautomatically starts another byte.NoteIf a node is changed, this may result in a new process image structure. In thiscase 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.
