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72 •
Fieldbus coupler/controller
Review
3.2.6.1 Memory areas
The controller uses a memory space of 256 words (word 0 ... 255) for the
physical input and output data.
Attention
The physical I/O module data can only be read internal by the CPU. The data
must be copyed into the PFC variables via the IEC 61131-3 program, in order
to be processed by the Neuron-Chip and accessed from the fieldbus side.
The controller is assigned an additional memory space for mapping the PFC
variables defined according to IEC 61131-3. This extended memory space
(word 256 ... 511 each) is used to map the PFC variables behind the physical
process image.
fieldbus
Fig. 3-5: Memory areas and data exchange for a fieldbus controller
1
2
3
4
Programmable fieldbus controller
memory area
for input
variable data
word 256
3
3
PFC
nvi
input
variables
word 511
memory area
for output
variable data
word 256
4
PFC
nvo
output
variables
word 511
The data of the input modules can only be read internal by the CPU. Via
the IEC 61131-3 program they can be processed or directly copyed on PFC
output variables.
In the same manner, writing to the output modules is only possible from
the CPU.
Transferring data from the fieldbus side to the controller is made using net-
work input variables (nivs). These are either processed in the Neuron-Chip
via the Neuron-C application or directly transmitted and written to the
memory area of the PFC input variables via the Dual-Port-RAM.
Subsequently the data can be read by the CPU in order to be processed.
Once the data has been processed through the IEC 61131-3 program, the
CPU writes the variable data to the memory area of the PFC output
variables.
The variables are transferred to the Neuron-Chip via the DPRAM and
processed in the Neuron-C application. Subsequently the data can be
accessed from the fieldbus side using network output variables (nvos).
memory area
for I/O module
input data
IEC 61131
word 0
program
input
modules
CPU
word 255
memory area
for I/O module
output data
word 0
output
modules
word 255
I/O modules
1
1
2
I
O
L
ON
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ORKS
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