Rockwell Automation 1771-VHSC , D17716.5.74 Very High S - Manual (Page 10)

1–2 Overview of the Very High Speed Counter Module
•
returns in status either count or frequency in binary or BCD
format
•
input counts as high as 999,999
•
up to 500KHz in period/rate or rate measurement frequency
modes
•
outputs can be tied to any counter
•
each output has a user-selectable on-off value
•
outputs can be tied back to an input for cascading
•
automatic default configuration
•
each counter has a user-selectable preset and rollover value
•
period/rate w/periodic outputs and period/rate w/dynamic outputs
can be used for totalization
The 1771-VHSC module operates in the following modes:
•
counter mode
•
encoder X1 mode
•
encoder X4 mode
•
period/rate mode
•
rate measurement frequency mode
•
continuous/rate mode
The operation of the module in these modes is described below.
The operation of encoder and counter modes is virtually identical.
The only difference between the two modes is in the type of
feedback used.
Use the counter mode if you need the module to read incoming
pulses from a maximum of four encoders (single-ended or
differential), counters, pulse generators, mechanical limit switches,
etc. and return them to the programmable controller as a binary or
BCD number (0-999,999). In counter mode, the module accepts only
one channel feedback.
Use the encoder modes if you need the module to read incoming
quadrature pulses and return them to the programmable controller as
a binary or BCD number (0-999,999). In these modes, the module
accepts two-phase quadrature feedback and counts up or down
depending upon the condition of the phase B input for each counter.
The operation of the module in the encoder/counter modes is as
follows:
Operation in Encoder or
Counter Mode