Technical data

Glossary
System Software for S7-300/400 System and Standard Functions- Volume 2/2
A5E00739858-01
Glossary-11
Priority
When you assign a priority to an organization block, you determine the interrupt
ability of the currently active user program so that high-priority events interrupt
lower-priority events.
Priority Class
The operating system of a CPU has a maximum of 28 priority classes, to which the
various organization blocks are assigned. The priority classes decide which OBs
can interrupt other OBs. If a priority class includes more than one OB, these do not
interrupt each other but are executed sequentially.
Process
The process is the part of the system in which the process variable is influenced by
the manipulated variable (by changing the level of energy or mass). The process
can be divided into the actuator and the actual process being controlled.
t
Process
t
LMN
PV
PV
LMN
Program Execution, Event-Controlled
With event-controlled program execution, the running of the cyclic user program is
interrupted by start events (priority classes). If a start event occurs, the block
currently being executed is interrupted before the next instruction and an assigned
organization block called and executed. Cyclic program execution then continues
from the point of interruption.
Proportional Actuator
Pulse duration modulation
Pulse Duration Modulation
Pulse duration modulation is a method of influencing the manipulated variable at a
discontinuous output. The calculated manipulated value as a percentage is
converted to a proportional signal pulse time Tp at the manipulated variable output,
for example, 100 % Tp = TA or = CYCLE.