Defining The Run Sequence - Siemens SIMATIC S7 F Manual

Programming
5. Close the "Select Structure Element" dialog box.
Result: The new value is displayed on the I/O.
See Also
F-Data Types
5.3.4

Defining the Run Sequence

Run-Time Properties
The run-time properties of a block define the position of this block in the
chronological processing sequence within the overall structure of the PLC. These
properties are decisive in the behavior of the PLC with regard to response times,
dead times or the stability of time-dependent structures such as control loops.
Each block receives default run-time properties when it is inserted. To do this, you
put it into a task at a position you can set. You can change this installation position
and other attributes to suit your requirements at a later date.
Run Sequence Within a Run-time Group
Note
The run sequence is checked at the beginning of compilation of the Safety
Program. The following F-Blocks are placed in the correct run sequence
automatically when the Safety Program is compiled:
You must arrange your blocks in following sequence:
•
F Input Channel Drivers (F_CH_DI, F_CH_AI)
•
All other F-Blocks not listed in the Note above
•
F Output Channel Drivers (F_CH_DO)
After the program is compiled for the first time (or modified), the CFC editor will
automatically place (or adjust) system level run-time groups necessary for the
Safety Program operation. These run-time groups have the '@' symbol preceding
the name of the run-time groups. These run-time groups contain the following
function blocks that are placed automatically:
5-14
•
F Control Blocks including F Module Driver Blocks
•
Blocks for F Communication Between CPUs
•
F-System Blocks
•
Blocks for Converting Data Between Standard and Safety
Sections
Fail-Safe Systems
A5E00085588-03