Fieldbus coupler/controller |
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Fieldbus controller 750-819 |
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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 |
Data width = 1 Bit / channel |
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Analog input modules |
Digital input modules |
Analog output modules |
Digital output modules |
Input modules for thermal elements |
Digital output modules with diagnosis (2 Bit / channel) |
Input modules for resistance sensors |
Power supply modules with fuse holder / diagnosis |
Pulse width output modules |
Solid State power relay |
Interface module |
Relay output modules |
Up/down counter |
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I/O modules for angle and path measurement |
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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 process 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.
Modular I/O System
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