Horner APG XL7 OCS - Manual (Page 45)

XL7 User Manual
11.3 High Speed Counter (HSC) Functions
The XL7 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 page 49).
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.
The totalizer supports the following modes:
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 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. 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.
Page 45 of 110