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Fieldbus coupler/controller
Review
3.2.5 Process image
Attention
The DPRAM of the fieldbus controller 750-819 does not contain the process
image but the PFC variables from the IEC 61131-3 program. The module
data must be copyed on the PFC variables via the IEC 61131-3 application
program, in order to be processed by the Neuron-Chip.
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 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.
Data width = 1 Word / channel
Analog input modules
Analog output modules
Input modules for thermal elements
Input modules for resistance sensors
Pulse width output modules
Interface module
Up/down counter
I/O modules for angle and path measurement
Tab. 3-1: I/O module data width
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 I/O modules is separated form the local input and output proc-
ess image in the sequence of their position after the coupler 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
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.
Data width = 1 Bit / channel
Digital input modules
Digital output modules
Digital output modules with diagnosis (2 Bit / channel)
Power supply modules with fuse holder / diagnosis
Solid State power relay
Relay output modules
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