Technical data

Basics of Designing a Program Structure
4.2 Blocks in the User Program
Programming with STEP 7
84 Manual, 05/2010, A5E02789666-01
Cycle Monitoring Time
With STEP 7, you can modify the default maximum cycle monitoring time. If this time expires, the
CPU either changes to STOP mode or OB80 is called in which you can specify how the CPU
should react to this error.
Minimum Cycle Time
With STEP 7, you can set a minimum cycle time for S7-400 CPUs and the CPU 318. This is useful
in the following situations:
• When the interval at which program execution starts in OB1 (main program scan) should
always be the same or
• When the process image tables would be updated unnecessarily often if the cycle time is too
short.
The following figures show the function of the cycle monitoring time in program processing in CPUs
up to 10/98 and in CPUs from 10/98.