User Manual User Manual

2 Rockwell Automation Publication 1794-UM010D-EN-E - July 2013
Overview of the Very High Speed Counter Module
The module features include:
• 2 counters configurable for 3 encoder modes, counter mode, period/rate
mode, continuous/rate mode, rate measurement and pulse width
modulation (PWM)
• 4 outputs, isolated in pairs
• outputs are current-sourcing at 5 or 12…24V DC (0.5 mA max @ 5V; 1 A
max @ 12…24V)
• single-ended or differential inputs
• 2-phase encoder inputs up to a frequency of 250 KHz (X 4 mode)
• single-phase counter inputs up to a frequency of 1 MHz
• input voltage range of 5 or 24V DC
• returns input as count or frequency in binary format
• input counts as high as 16,777,215
• up to 1 MHz in period/rate or rate measurement frequency modes
• outputs can be tied to any or all counter windows
• each output has a user-selectable on-off value
• outputs can be tied back to an input for cascading
• each counter has a user-selectable preset and rollover value
• totalization is provided in period/rate, continuous/rate and rate
measurement modes
• module can continue counting without flexbus power (after configuration)
• outputs have safe state values which can be applied when there is a network
failure or the PLC is switched to PROGRAM mode
• pulse width modulation (PWM) mode is available
The 1794-VHSC module operates in the following modes:
• counter mode
• encoder X1 mode
• encoder X2 mode
• encoder X4 mode
• period/rate mode
• continuous/rate mode
• rate measurement frequency mode
• pulse width modulation (PWM)
Encoder or Counter Mode
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 2 encoders (single-ended or differential), counters, pulse generators,
mechanical limit switches, etc. and return them to the programmable controller
as a binary number (0…16,777,215).