Siemens SIMATIC S7-200, Системное руководство

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Program instructions
7.7 Pulse output
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
287
7.7.2 Pulse train output (PTO)
PTO provides a square wave with a 50% duty cycle output for a specified number of pulses
at a specified frequency. Refer to the figure below. PTO can produce either a single train of
pulses or multiple trains of pulses using a pulse profile. You specify the number of pulses
and the frequency:
• Number of pulses: 1 to 2,147,483,647
•
Frequency:
– 1 to 100,000 Hz (multiple-segment)
– 1 to 65,535 Hz (single-segment)
Use the following formula to convert from cycle time to frequency:
F = 1 / CT
where:
F Frequency (Hz)
CT Cycle time (seconds)
See the following table for pulse count and frequency limitations:
Table 7- 15 Pulse count and frequency in the PTO function
Pulse count / frequency Reaction
Frequency < 1 Hz Frequency defaults to 1 Hz
Frequency > 100,000 Hz Frequency defaults to 100,000 Hz
Pulse count = 0 Pulse count defaults to 1 pulse
Pulse count > 2,147,483,647 Pulse count defaults to 2,147,483,647 pulses
Note
When using a PTO with very short cycle times (high frequencies), you should take into
account the switching delay specifications for the output points and how the switching delay
can affect the duty cycle. See Appendix A for the digital output switching delay for your CPU.
The PTO function allows the "chaining" or "pipelining" of pulse trains. When the active pulse
train is complete, the output of a new pulse train begins immediately. This allows continuity
between subsequent output pulse trains.