Rockwell Automation 1755-OF8 GuardPLC Controller Systems - Manual (Page 109)

Publication 1753-UM001C-EN-P - March 2010 109
High-Speed Counters Chapter 12
Understand Counter
Module Configuration The high-speed counters can be configured for three counting modes:
Counter mode with manual direction, Counter mode with direction
and reset, and Decoder mode (Gray codes).
Counter Mode/Manual Direction
The simplest mode of operation is pulse counting with manual
direction. It can be used, for example, in connection with a light
barrier where counting events are to be recorded. The direction of
counting is determined by the routine.
The count begins at 0 and is incremented or decremented by 1 at each
negative transition of the counting pulse. The resolution of the
counter is 24 bits. This results in a value range from 0…16,777,215.
The counting pulse must be bounce free and must not exceed the
maximum frequency of 1 MHz for a GuardPLC 2000 controller or
100 kHz for a GuardPLC 1200 or 1800 controller. The counter input
can be set to a voltage of 5V or 24V via the software.
To be sure that the counter functions correctly, configure these
parameters.
Parameter Setting
Cnt[0x].5/24V Mode true for 24V
or
false for 5V
You must configure this parameter with a constant.
Cnt[0x].Auto Advance Sense (optional according to routine)
false to count only up or only down based upon the
direction bit
Cnt[0x].Direction (optional according to routine)
true to decrement (counts from 16,777,215 downward)
or
false to increment
Cnt[0x].Gray Code (optional according to routine)
false
Cnt[0x].Reset (optional according to routine)
true
If this parameter is set to false, the counter value is
reset to 0.