Siemens SIMATIC S7 System Manual page 318
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102BTechnology instructions
9.1 High-speed counter
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 9- 5
Counting modes for HSC
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
For an encoder: Phase Z, Home
1
318
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.
Input 1
Clock
Clock
Clock up
Phase A
Input 2
Input 3
(Optional:
-
direction)
Reset
Direction
-
Reset
Clock down
-
Reset
Phase B
-
Reset
1
Function
Count or frequency
Count
Count or frequency
Count
Count or frequency
Count
Count or frequency
Count
S7-1200 Programmable controller
System Manual, 11/2011, A5E02486680-05
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- Introducing the S7-1200 Plc
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