Technical data

SFCs for Handling Time-of-Day Interrupts
System Software for S7-300/400 System and Standard Functions - Volume 1/2
9-2 A5E00709327-01
9.2 Characteristics of SFCs 28 to 31
What Happens If...
The following table lists a number of different situations and explains the effect they
have on a time-of-day interrupt.
If ... Then ...
A time-of-day interrupt is set (by calling SFC 28;
SET_TINT)
The current time-of-day interrupt is canceled.
The time-of-day interrupt is canceled (by calling
SFC 29; CAN_TINT)
The start date and time are cleared. The time-of-day
interrupt must then be set again before it can be
activated.
The time-of-day interrupt OB does not exist
when it is called.
The priority class error is generated automatically,
which means that the operating system calls OB85.
If OB85 does not exist, the CPU changes to STOP.
The real-time clock is synchronized or the clock
adjusted forward
If the start date/time is skipped because the clock is
moved forward:
• The operating system calls OB 80
1
.
• Following OB 80, every skipped time-of-day
interrupt
OB is called (once, regardless of the number of
periods that were skipped) provided that it was not
manipulated in OB80
2
.
If OB 80 does not exist, the CPU changes to STOP.
The real-time clock is synchronized or the clock
adjusted back
S7-400-CPUs and CPU 318:
If the time-of-day interrupt OBs had already been called
during the time by which the clock has been moved
back, they are not called again the second time around.
S7-300-CPUs: The affected the time-of-day interrupt
OBs are all executed.
1) OB 80 contains encoded start event information, indicating which time-of-day interrupt OBs could
not be called due to moving the clock forward. The time in the start event information corresponds to
the time adjusted forward.
2) The time in the start event information of the time-of-day interrupt activated later after being skipped
corresponds to the start time of the first skipped time-of-day interrupt.
Warm Restart or Cold Restart
During a warm restart or a cold restart, all the time-of-day interrupt settings made in
the user program by SFCs are cleared.
The parameters set using STEP 7 are then effective.