Technical data

Table Of Contents
System Software for S7-300/400 System and Standard Functions - Volume 2/2
A5E00739858-01
25-1
25 IEC Timers and IEC Counters
25.1 Generating a Pulse with SFB 3 "TP"
Description
SFB 3 "TP" generates a pulse with the length PT. The timer runs only in the
STARTUP and RUN modes.
A rising signal edge at input IN starts the pulse. Output Q remains set for the time
PT regardless of changes in the input signal (in other words even when the IN input
changes back from 0 to 1 before the time PT has expired).The ET output provides
the time for which output Q has already been set. The maximum value of the ET
output is the value of the PT input. Output ET is reset when input IN changes to 0,
however, not before the time PT has expired.
SFB 3 "TP" complies with the IEC 1131-3 standard.
The operating system resets the instances of SFB 3 "TP" during a cold restart. If
you want instances of this SFB to be initialized following a warm restart, you must
call SFB 3 with PT = 0 ms in OB100. If instances of this SFB are located within
another block, you can reset these instances, for example, by initializing the higher-
level block.
Timing Diagram
PT
ET
Q
IN
PT
PTPT