Siemens S7-1200 - Time Delay Interrupts

Extended instructions
8.4 Interrupts
S7-1200 Programmable controller
342 System Manual, 03/2014, A5E02486680-AG
8.4.4
Time delay interrupts
You can start and cancel time delay interrupt processing with the SRT_DINT and CAN_DINT
instructions, or query the interrupt status with the QRY_DINT instruction. Each time delay
interrupt is a one-time event that occurs after the specified delay time. If the time delay event
is cancelled before the time delay expires, the program interrupt does not occur.
Table 8- 108 SRT_DINT, CAN_DINT, and QRY_DINT instructions
LAD / FBD
SCL
Description
ret_val := SRT_DINT(
ob_nr:=_int_in_,
dtime:=_time_in_,
sign:=_word_in_);
SRT_DINT starts a time delay interrupt that
executes an OB when the delay time specified by
parameter DTIME has elapsed.
ret_val := CAN_DINT(
ob_nr:=_int_in_);
CAN_DINT cancels a time delay interrupt that has
already started. The time delay interrupt OB is not
executed in this case.
ret_val := QRY_DINT(
ob_nr:=_int_in_,
status=>_word_out_);
QRY_DINT queries the status of the time delay
interrupt specified by the OB_NR parameter.
Table 8- 109 Data types for the parameters
Parameter and type
Data type
Description
OB_NR IN OB_DELAY Organization block (OB) to be started after a time-delay: Select from
the available time-delay interrupt OBs that were created using the "Add
new block" project tree feature. Double-click on the parameter field,
then click on the helper icon to see the available OBs.
DTIME
1
IN
Time
Time delay value (1 to 60000 ms)
SIGN
1
IN Word Not used by the S7-1200: Any value is accepted. A value must be
assigned to prevent errors.
RET_VAL
OUT
Int
Execution condition code
STATUS OUT Word QRY_DINT instruction: Status of the specified time-delay interrupt OB,
see the table below
1
Only for SRT_DINT
Operation
The SRT_DINT instruction specifies a time delay, starts the internal time delay timer, and
associates a time delay interrupt OB subprogram with the time delay timeout event. When
the specified time delay has elapsed, a program interrupt is generated that triggers the
execution of the associated time delay interrupt OB. You can cancel an in-process time
delay interrupt before the specified time delay occurs by executing the CAN_DINT
instruction. The total number of active time delay interrupt events must not exceed four.