Technical data

58 • BACnet/IP Controller 750-830
Process Image
WAGO-I/O-SYSTEM 750
BACnet/IP Controller
Note
If a node is changed or expanded, this may result in a new process image
structure. The process data addresses would then change. In case of an ex-
pansion, the process data of all previous modules has to be taken into ac-
count.
A memory range of 256 words (word 0 ... 255) is initially available in the con-
troller for the process image of the physical input and output data.
For the image of the MODBUS/PFC variables, the memory range of words
256 ... 511 is reserved, meaning the image for the MODBUS/PFC variables is
created behind the process image for the bus module data
If the quantity of module data is greater than 256 words, all the physical input
and output data above this value is added to the end of the current process im-
age in a memory range; i.e., attached behind the MODBUS/PFC variables
(word 512 ... 1275).
The range from word 1276 to word 1531 is not available to the user.
The subsequent range, starting from word 1532, is reserved for future protocol
expansion and other PFC variables.
For all WAGO fieldbus controllers, access by the PLC (CPU) to process data
is made regardless of the fieldbus system; access is always conducted through
an application-related IEC 61131-3 program.
How the data is accessed from the fieldbus side depends on the fieldbus, how-
ever.
A MODBUS/TCP Master can access the data for the BACnet/IP controller via
the MODBUS functions that are implemented.
Additional Information
For a detailed description of these fieldbus-specific data access methods, re-
fer to the section "MODBUS-Functions".