Technical data

Note
With respect to time-driven program execution, remember the
special functions
OB 120, OB 121, OB 122 and OB 123 with
which you can disable or delay the processing of time interrupts
for a particular program section. (This is possible either for all
programmed time interrupts or for individual time interrupts.)
The "faster" a time-driven program processing level is, the greater
the danger of time interrupt collisions. If you have time interrupts
with short time bases (e.g. the 10 ms and the 20 ms time
interrupts) it is normally necessary to select interruption at
operation boundaries. This means that the closed loop controller
interrupt and the process interrupt must also be set to interrupt at
operation boundaries (see Chapter 7, Assigning Parameters to
DX 0).
4.5.3
CLOSED LOOP
CONTROLLER INTERRUPT:
Processing Closed Loop
Controllers
In the CPU 928B, apart from cyclic, time and process interrupt
program execution, it is also possible to process closed loop
controllers. You select intervals (= sampling time) at which the cyclic
or time-driven program execution is interrupted and the controller is
processed. Following this, the CPU returns to the point at which the
cyclic or time-driven program was interrupted and continues
execution.
Triggering A closed loop controller interrupt is triggered when the sampling time
you have selected elapses.
System program activities
•• It manages the user interface for closed loop controller processing.
•• It updates the controller process image.
User interface: standard
function block "closed loop
controller structure R64"
When processing a controller, the R64 standard function block is
called as the user interface. In conjunction with the controller
parameter assignment block DB 2, this allows up to 64 controllers to
be processed.
You assign a specific data block for each controller. In data block DB
2, known as the "controller list" you specify which controllers are to
be processed by the system program at which point in time. DB 2 is
reserved for this task.
(When assigning parameters, starting up and testing the R64 standard
FB, you are supported by a special program package: "COMREG",
see Catalog ST 59.)
RUN Mode
CPU 928B Programming Guide
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