Outputs, Enabling and forcing outputs, Assigning outputs to counter windows – Rockwell Automation 1794-VHSC 1794 FLEX I/O Very High Speed Counter Module User Manual User Manual
Page 21: Operation of outputs
Rockwell Automation Publication 1794-UM010D-EN-E - July 2013
13
Overview of the Very High Speed Counter Module
Outputs
The 1794-VHSC module has 4 outputs, isolated in groups of 2. Each of the
outputs is capable of sourcing current and will operate between 5 and 24V DC.
You must connect an external power supply to each of the outputs. The outputs
can source 1 A DC alone or in combination. The outputs are hardware-driven
and will turn on in about 25 s when the appropriate count value has been reached.
Enabling and Forcing Outputs
Outputs may be forced on or off independent of count or frequency value. To
force the outputs, they must first be enabled. Enabling the outputs is done
through a data table word 1, bits 1, 5, 9 and 13 (see Figure
Speed Counter Module Image Table Mapping on page 35
). Once the outputs
have been enabled, they may be forced on by setting bits 0, 4, 8 or 12 in word 1.
The outputs can be forced off by setting the enable bit to 0.
Assigning Outputs to Counter Windows
By setting bits in the configuration block, you can assign the outputs on the
module to any of the various counter windows. You can assign any output to any
count window with no restrictions.
Operation of Outputs
When the outputs for the 1794-VHSC module are enabled and assigned to a
counter window they operate in an ON-OFF fashion. For example, assume that
the module were programmed to turn ON an output when a count value of 2000
was reached. Further, assume that the user desired to have the output remain
energized for a period of 3000 counts and then turn OFF. The end result would
be that the outputs would turn ON at count of 2000, would remain energized for
3000 additional counts, and would turn OFF at 5000 counts. The ON and OFF
values are circular around zero (see Figure
).
On-Off Operation of Output
Using output 0 as an example, when the value in Counter ON Value is less than
the value in Counter OFF Value, the output turns on at 2000 and off at 5000. If
the value in Counter ON Value is greater than the value in Counter OFF Value,
the output turns off at 2000 and on at 5000 (see Figure
Output turns on at
count value of 2000
Output remains energized for
3000 additional counts
Output turns off at
count value of 5000