Horner APG XL4 OCS - Manual (Page 50)

CH.11 MAN0964-01-EN
June 29, 2012 Page 50 of 122
11.3 High Speed Counter (HSC) Functions
The XL4 supports two very high speed, configurable counters. There are four dedicated inputs that can
be configures 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 (see mapping below).
11.3.1 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 that 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. Please see section 11.2 for a description of these functions.
11.3.2 Totalize
In totalize mode, the accumulator is simply incremented or decremented each time the input
transitions in a specific direction.
There are five different modes the totalizer can run:
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 that 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 that 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 one(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. Please
see section 11.2 for details.
11.3.3 Pulse Width Measurement
In pulse width measurement mode, the high-speed input can measure the width of a pulse stream
in one of two modes and provides a continuous indication of the last sampled value. In this mode
the Disable and Latch special functions are allowed. Please see section 11.2 for a description of
these functions.