Start-Up Program Processing - Siemens S5-100U User Manual

Introduction to STEP 5
7.4.2

START-UP Program Processing

In the START-UP mode, the operating system of the CPU automatically calls up a start-up OB if the
OB has been programmed.
• OB21 is called up for a manual cold restart.
• OB22 is called up for an automatic cold start after power recovery if the programmable controller
was previously in the RUN mode.
If you have programmed start-up OBs, they are processed before the cyclic program processing
occurs. The start-up OB program is appropriate, for example, for a one-time presetting of certain
system data. If the appropriate start-up OB is not programmed, the programmable controller jumps
directly to the RUN mode. See section 4.1.2.
Features of the start-up blocks (OB21, OB22):
• The red and green LEDs light.
• Timers are processed.
• Scan monitoring is not activated.
• Interrupts are not processed.
Operating mode switch set from STOP
to RUN; Programmer command RUN
Clear the process image I/O table,
the non-retentive timers,
counters, and flags.
Interpret DB1
Processing OB21
1 This is the procedure if the programmable controller was in the RUN mode when the power went off,
if the mode switch was still on RUN when the power was restored, and if the battery was inserted. If
the battery was not inserted, you must insert a memory submodule containing the valid blocks.
2 For CPU 103 version 8MA03 and higher
7-24
2
Enable the outputs
Read in the PII
Process OB1
Read out the PIQ
Figure 7-12. Setting the Start-Up Procedure
Power recovery
Clear the process image I/O table,
the non-retentive timers,
counters, and flags.
Interpret DB1
Processing OB22
S5-100U
1
Cold
restart
routine
2
START-
UP
RUN
EWA 4NEB 812 6120-02