Siemens SIMATIC S5 Manual page 43

IP 266
The "External Start Enable" signal starts the first block of the machining
program.
A short pulse of the "Position Reached" signal appears between blocks that
are not interconnected by a "flying change".
Switching function M99 is active in the sixth block.
The block has executed. Since the "External Start Enable" signal disables
execution of blocks containing machining operations or dwells, program
execution is interrupted.
The "External Start Enable" signal does not interrupt offsets or corrections.
The "External Stop" signal initiates maximum-rate deceleration.
The drive is at a standstill. The machining program is terminated and the
"Machining program executing" signal is removed.
Example 3
Three jobs are started in succession.
Job 1: Absolute target position
Job 2: Relative target position
Job 3: Relative target position
Start of job 1
Job
External
Start
External
Stop
Position
Reached
signal
Executing
Axis finished
Job executing;
axis outside tolerance limits of zero-speed
EWA 4NEB 812 6057-02
Technical Description of the IP 266
Start of job 2 Start of job 3
Job is aborted
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