120 Rockwell Automation Publication 2080-UM002G-EN-E - March 2015
Chapter 8 Use the High-Speed Counter and Programmable Limit Switch
What is High-Speed
Counter?
High-Speed Counter is used to detect narrow (fast) pulses, and its specialized
instructions to initiate other control operations based on counts reaching preset
values. These control operations include the automatic and immediate execution
of the high-speed counter interrupt routine and the immediate update of outputs
based on a source and mask pattern you set.
The HSC functions are different than most other controller instructions. Their
operation is performed by custom circuitry that runs in parallel with the main
system processor. This is necessary because of the high performance requirements
of these functions.
Features and Operation
The HSC is extremely versatile; you can select or configure the master HSC for
any one of ten (10) modes and the sub HSC for any one of five (5) modes of
operation. See HSC Mode (HSCAPP.HSCMode)
on page 126 for more
information.
Some of the enhanced capabilities of the High-Speed Counters are:
• 100 kHz operation
• Direct control of outputs
• 32-bit signed integer data (count range of ± 2,147,483,647)
• Programmable High and Low presets, and Overflow and Underflow
setpoints
• Automatic Interrupt processing based on accumulated count
• Change parameters on-the-fly (from the user control program)
The High-Speed Counter function operates as described in the following
diagram.
High Speed Counter Operation
+2,147,483,647 maximum
-2,147,483,648 minimum
Overflow
High Preset
0
Low Preset
Underflow
HscAppData.OFSetting
HscAppData.HPSetting
HscAppData.LPSetting
HscAppData.UFSetting
Variable
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