Technical data

Testing Using Program Status
21.3 What You Should Know About the HOLD Mode
Programming with STEP 7
472 Manual, 05/2010, A5E02789666-01
21.3 What You Should Know About the HOLD Mode
If the program encounters a breakpoint, the programmable controller goes into the HOLD operating
mode.
LED Display in HOLD Mode
• LED RUN flashes
• LED STOP is lit
Program Processing in HOLD Mode
• In HOLD mode, no S7 code is processed, meaning no priority classes are processed any
further.
• All timers are frozen:
- No timer cells are processed
- All monitoring times are paused
- The basic clock rate of the time-controlled levels are paused
• The real time clock continues to run
• For safety reasons, the outputs are always disabled in HOLD mode ("output disable").
Behavior following Power Supply Failure in HOLD Mode
• Programmable controllers with battery backup change to STOP mode and remain there
following a power supply failure during HOLD mode and a subsequent return of power. The
CPU does not execute an automatic restart (warm restart). From STOP mode you can
determine how processing continues (for example, by setting/resetting breakpoints, executing a
manual restart).
• Programmable controllers without battery backup are not "retentive" and therefore execute an
automatic warm restart when power returns, regardless of the previous operating mode.