Siemens SIMATIC S7-1200 Manual page 118

Programming made easy
6.6 High-speed counter (HSC)
Selecting the functionality for the HSC
All HSCs function the same way for the same counter mode of operation. There are four
basic types of HSC:
● Single-phase counter with internal direction control
● Single-phase counter with external direction control
● Two-phase counter with 2 clock inputs
● A/B phase quadrature counter
You can use each HSC type with or without a reset input. When you activate the reset input
(with some restrictions, see the following table), the current value is cleared and held clear
until you deactivate the reset input.
● Frequency function: Some HSC modes allow the HSC to be configured (Type of
reported value will be an intermediate between the highest and lowest frequency
occurring during the measuring period. The frequency is always reported in Hertz (pulses
per second) regardless of the frequency-measuring-period setting.
● Counter modes and inputs: The following table shows the inputs used for the clock,
direction control, and reset functions associated with the HSC.
The same input cannot be used for two different functions, but any input not being used
by the present mode of its HSC can be used for another purpose. For example, if HSC1
Table 6- 29
Type
Single-phase counter with
internal direction control
Single-phase counter with
external direction control
Two-phase counter with 2
clock inputs
A/B-phase quadrature
counter
118
counting) to report the frequency instead of a current count of pulses. Three different
frequency measuring periods are available: 0.01, 0.1, or 1.0 seconds.
The frequency measuring period determines how often the HSC calculates and reports a
new frequency value. The reported frequency is an average value determined by the total
number of counts in the last measuring period. If the frequency is rapidly changing, the
is in a mode that uses built-in inputs but does not use the external reset (I0.3), then I0.3
can be used for edge interrupts or for HSC2.
Counting modes for HSC
Input 1 Input 2
Clock (Optional:
direction)
Clock Direction
Clock up Clock down
Phase A Phase B
Input 3 Function
- Count or frequency
Reset Count
- Count or frequency
Reset Count
- Count or frequency
Reset Count
- Count or frequency
Phase Z Count
Manual, 11/2011, A5E02486774-04
Easy Book