Operating Modes; Start-Up And Program Tests - Siemens SIMATIC S5-90U System Manual

Start-Up and Program Tests

4.1.2

Operating Modes

"STOP" Operating Mode
• The program is not executed.
• The current values for timers, counters, flags, and process images are saved when the "STOP"
operating mode begins.
• The onboard outputs and the output modules are disabled; i.e. the digital outputs have the "0"
signal state and the analog outputs are de-energized.
• The onboard counters are not activated.
• The process images, timers, non-retentive flags and counters are set to "zero" during the
transition from "STOP" to "RUN."
"RUN" Operating Mode
• The program is processed cyclically.
• Already started timers continue to run.
• Signal states for the onboard inputs and the input modules are read in.
• The onboard outputs and output modules are addressed.
• The "RUN" operating mode can also be set after an "OVERALL RESET", that is, when the
program memory is empty.
"RESTART" Operating Mode
• The operating system processes DB1 and accepts the parameters (see Section 9.1).
• Restart organization block OB21 or OB22 is processed (see Section 7.4.1).
• The amount of time the restart requires is not limited since the scan time monitor is not
activated.
• Neither time-controlled program processing nor interrupt-controlled program processing is
possible.
• The onboard inputs and onboard outputs can be addressed by either the L PB/L PW operation
or the T PB/T PW operation during start-up.
• The external input modules and output modules are disabled during start-up.
Changing Operating Modes
A change in operating mode can be caused by the following.
• Actuation of the operating mode switch.
• A programmer, if the operating mode switch on the programmable controller is set to "RUN".
• Malfunctions that cause the programmable controller to go into the "STOP" operating mode (see
Chapter 5).
4-2
S5-90U/S5-95U
EWA 4NEB 812 6115-02b