Rockwell Automation 1734-VHSC24 Very High-Speed Counter Modules User Manual - Manual (Page 12)

Publication 1734-UM003B-EN-P - August 2005
1-2 About the Modules
The outputs are rated to source 0.5A at 10 to 28.8V dc. The output
may be tied to an input. This lets you cascade counters of multiple
1734-VHSC modules. The counter has 4 user-selectable On-Off values
(windows) associated with it. Tie either output to any or all of the
window signals.
Operating Modes The modules operate in the modes shown in the table.
The operation of the counter and encoder modes is nearly identical.
The difference between the two modes is in the type of feedback
(single-phase versus two-phase) for the count direction (up or down).
In encoder mode, a transition is expected on the B input for
counting to proceed in a direction; whereas, in counter mode, the B
input may be left at a static level.
You select all operating modes by writing appropriate configuration
data to the module.
Counter Mode
The counter mode reads incoming pulses and returns a binary
number (0 - 16,777,215
max
) to the POINTBus. The counter mode only
accepts single-phase inputs. The module determines the Phase B
input state, and counts up or down accordingly.
Mode Description
Counter Mode Read read incoming single-phase pulses, return a
binary count.
Encoder Mode Read incoming two-phase quadrature pulses, return
a binary count.
Period/Rate Mode Count internal clocks during the On period, return a
frequency. Outputs updated only at the end of the
period.
Continuous/Rate Mode Count internal clocks during the On period, return a
frequency. Outputs are updated continuously during
the period.
Rate Measurement Mode Read pulses during the sample period, return a
frequency.
PWM Mode (pulse width
modulation) Generate a pulse width modulated signal.