Memory Areas - WAGO 750-872/020-000 Manual

56 • Fieldbus Controller
Fieldbus Controller 750-872/020-000
application program, whereby the data addressing is different than the fieldbus
addressing.

3.1.6.1 Memory Areas

Fig. 3.1-8: Memory Areas and Data Exchange for a Fieldbus Controller
The PFC's process image contains the physical data of the I/O modules in
memory words 0 to 255 and 512 to 1275.
(1) Reading data of the input modules is possible from both the controller's
(2) In the same manner, writing data to output modules is possible from both
The controller's process image also contains variables called "PFC Variables".
These variables are allocated based on the fieldbus protocols. The MODBUS
TCP PFC variables are stored in memory from word 256 to 511. Ethernet IP
PFC variables are stored in memory from word 1276 to 1531. The memory
area above word 1531 is reserved for future protocols.
(3) The PFC input variables are written into the input memory space from the
(4) The variables processed by the controller's CPU , via an IEC 61131-3
Programmable Fieldbus Controller
fieldbus
master
CPU and from the fieldbus master (See Figure 3-8).
the controller's CPU and from the fieldbus master.
fieldbus master and can be read by the controller's CPU for further
processing.
application program, can be written to the PFC Variables and then read by
the fieldbus master.
memory area
for input data
word 0 1 1
input
modules
word 255
3 3
word 256
IEC 61131-
PFC program
input
variables
CPU
word 511
memory area
for output data
2
word 0
output
modules
2
word 255
word 256
4
PFC
4
output
variables
word 511
I/O modules
I
O
g012938e
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP