Frequency And Pulse Width Measurement; Special Signals - Siemens SMP16-SFT251 Technical Description

Features
2.5.2

Frequency and Pulse Width Measurement

With frequency and pulse width measurement, the reference gate signal must be at least twice as long
as the maximum expected cycle duration of the frequency to be measured.
External frequency
(input A)
Gate signal
(input B)
Figure 2.3 Time relationships with frequency and pulse width measurement
t7 Clock pulse high/low time
t6 Gate time when the external clock pulse is used
t6 Gate time when the internal clock pulses are used
t8 Cycle time of the internal clock pulses:
1.25 MHz
2.5 MHz
2.0 MHz
4.0 MHz
2.5.3

Special Signals

ZS00, ZS10, ZS20, ZS30
ZS01, ZS11, ZS21, ZS31
Figure 2.4 Time relationships of the special signals
t4
t5
14
t7 t7
t5
High edge to high edge
Pulse width
t6
125 nsec (min.)
2 x t7 (min.)
t8 (min.)
800 nsec
400 nsec
500 nsec
250 nsec
t4
400 nsec (min.)
250 nsec (min.)
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SMP16-SFT251