Siemens SIMATIC PCS 7 Configuration page 61

4 Function mechanisms
4.1 Example of a flowchart
Description of the upper part of the flowchart
In the upper part, two temperature measurements are transferred by two encoders
via two redundant AI modules and written via two addresses (EW512, EW560) in
the process image partition of the inputs.
Depending on the setting of the transfer value (see Additional Parameters
Table 3–5 point 7), the smaller or greater value is written in the user program on
the channel block CH_AI via the corresponding "TI111" symbol.
The @-charts, where the blocks from the redundant IO CGP (RED_IN,
RED_STATUS, etc.) and from the PCS 7 Library (OR_M16_C) are placed, allow
the diagnostic and redundancy analysis to be performed. The block OR_M16_C
transmits the corresponding diagnostic or redundancy status to the channel block
CH_AI.
This automatically leads to the corresponding redundancy message behavior,
depending on the status (OR_M16_C, see below).
Description of the lower part of the flowchart
In the lower part of the flowchart, a control valve is controlled by two redundant
analog output modules.
Note Only analog output modules with current outputs can be operated redundantly
(0...20mA, 4...20mA). See chapter 2.3.4 "Analog output".
A value is written into the process image partition of the outputs from the channel
block CH_AO via the pre-configured symbol "QCTRL1". The @-charts and
especially the RED_OUT allow information to be analyzed and corresponding
output values to be given out by the system. This is done via the process image
partition of the outputs (addresses AW512 and AW544).
The value to be transferred is halved and each of the two channels transmits half
the value. If one of the channels or modules fails, this is detected and the
remaining channel or module transmits the full value.
This flowchart is repeated cyclically according to call and cycle time of the OBs
used (in this case OB35 every 100 ms).
Configuration of Redundant I/O Modules
Entry-ID: 28430682, V2.0, 03/2015
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