Systemsoftware
2-24
System- and communication configuring D7-SYS - SIMADYN D
Edition 03.2001
2.1.7.1 Implementing the process image
The system mode is used to implement the process image before a task
is computed. In the following Fig. 2-6 Sequence of the function block
computation in the system- and standard modes, the sequence in which
the function blocks are executed in the system- and standard mode is
illustrated in cyclic operation (CPU in the RUN status). In this example,
functions blocks 10 and 30 in the system mode are computed within the
process image so that the results can be subsequently consistently used
in the standard mode.
System mode
Standard mode
10
30
Tx, Ix
Processing by the
operating system
Function block
Explanation of symbols:
Process image
Remaining cycle
10
20
30
35
40
Fig. 2-6
Sequence of the function block computation in the system- and standard modes
The system mode starts immediately after the initiating event (process
interrupt or basic clock cycle) in order to create a real time process
image. The execution between the jump into the operating system up to
the end of the system mode can only be interrupted by a higher priority
system mode. Among other things, function blocks with access to the
periphery are computed.
System mode
