Glossary
S7-GRAPH for S7 300/400 Programming Sequential Control Systems
Glossary-2 C79000-G7076-C526-01
Execution time
The execution time of an instruction is the time during which the instruction
(statement) is active; in other words is being executed.
Interlock
An interlock is a programmable condition within a step. An interlock influences the
execution of individual actions.
Ladder Logic branch
A Ladder Logic branch corresponds to an OR logic operation on elements in a
transition, supervision or interlock.
Normally open contact/normally closed contact
Normally-open contacts and normally-closed contact are bit logic operations. They
can be used as elements in transitions, supervisions or interlocks.
• The normally-open contact switches when the Boolean address is set.
• The normally-closed contact switches when the Boolean address is not set.
Process image
Memory area on the CPU in which the states of the inputs and outputs is entered.
• Process image input table (PII): PII
• Process image output table (PIQ): PIQ.
Processing time
The processing time is the time required by the CPU to execute an instruction
(action, condition) and is usually in the ms range per instruction.
Sequencer
A sequencer is the heart of a sequential control system. The program for step-by-
step execution of the sequential control system is created and executed here.
A sequencer consists of a series of steps and transitions that are activated in a
fixed order depending on the step enabling conditions.
An S7-Graph function block can contain up to eight sequencers.
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