MAN1106-07-EN_XL+_UserManual
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9.3
High Speed Counter (HSC) Functions
The XL+ supports two very high speed, configurable counters. There are four dedicated inputs
that can be configured to a number of different options. Each of the two counters can run in
one of five modes. Those modes are Totalizer, Frequency Counter, Pulse Width Measurement,
Period Measurement, and Quadrature measurement. For some modes, more than one HSC
input may be consumed. The measurement values are provided to ladder in a %AI register
(
9.3.1 Frequency
In frequency mode, the frequency of the input signal is written to the accumulator in terms of
Hertz (cycles/second). When using frequency mode, four update selections are provided
which specify the width of the sample window.
NOTE: Selecting a shorter sample window provides a quicker measurement (faster response)
but lowers the frequency accuracy (resolution) and increases the minimum frequency
measurement limit. In this mode the Disable and Latch special functions are allowed. Refer to
the
for a description of these functions.
9.3.2 Totalize
In totalize mode, the accumulator is simply incremented or decremented each time the input
transitions in a specific direction.
The totalizer supports the following modes:
Table 9.2
–
Modes supported by Totalizer
Internal
This mode ties the input to the counter to an internal 10MHz or
1MHz clock. The special functions can be used to accurately time
events.
Count Up
This increments the accumulator when the input is enabled.
NOTE: Two inputs can be assigned. Either input can cause the
counter to increment. The second input can also be disabled.
Count Down
This decrements the accumulator when the input is enabled.
NOTE: Two inputs can be assigned. Either input can cause the
counter to decrement. The second input can also be disabled.
Up/Down
(Input 1 Up/Input 2
Down)
In this mode, Input 1 (assigned to any of the four inputs)
increments the counter, while Input 2 (also assigned to any of the
4 inputs) decrements the counter.
Clk/Dir
(Input 1 Clk, Input 2
Dir)
This mode uses Input 1 as a clock signal to increment or decrement
the counter and then uses Input 2 to decide the direction. Input 2
disabled increments the counter, while Input 2 enabled
decrements the counter.
NOTE: The totalize mode enables the Disable, Latch, Preload, and Clear special functions.
Refer to the
for a description of these functions.
NOTE: Counter triggers off the rising edge of the signal.
