Rockwell Automation 1771-VHSC , D17716.5.74 Very High S - Manual (Page 9)

Chapter
1
Overview of the Very High
Speed Counter Module
This chapter gives you information on:
•
features of the VHSC module
•
how the module communicates with programmable controllers.
•
how the module operates
The VHSC module performs high speed counting for industrial
applications. The module is an intelligent block transfer I/O module
that interfaces signals with any Allen-Bradley programmable
controller that has block transfer capability. Block transfer
programming moves module status data from the module’s memory
to a designated area in the processor data table. It also moves
configuration words from the processor data table to the module
memory.
The VHSC module is a single-slot module that does not require an
external power supply. (Note: The outputs do require a power
supply.) After scanning the inputs and updating the outputs, the input
data is converted to a specified data type in a digital format to be
transferred to the processor’s data table on request. Command and
configuration data is sent from the programmable controller data
table to the module with a BTW instruction.
Features of the Module
The VHSC module counts pulses from encoders (such as
Allen-Bradley Bulletin 845H, K, F, P, E and L), pulse generators or
mechanical limit switches, proximity switches, etc. and returns either
a count or frequency in binary or BCD format.
The module’s features include:
•
4 input channels configurable for encoder mode, counter mode,
period/rate mode and continuous/rate mode
•
8 outputs, isolated in groups of 2
•
outputs are current-sourcing at 5 to 24V dc (2A maximum per
output)
•
single-ended or differential inputs
•
2-phase encoder inputs up to a frequency of 250KHz
•
single-phase counter inputs up to a frequency of 1MHz
•
input voltage range of 5 to 24V dc
Chapter Objectives
Module Description