Rockwell Automation 1755-OF8 GuardPLC Controller Systems - Manual (Page 107)

107 Publication 1753-UM001C-EN-P - March 2010 107
Chapter
12
High-Speed Counters
Introduction This chapter covers using counters in these systems:
•
GuardPLC 1200 controllers
•
GuardPLC 1800 controllers
•
GuardPLC 2000 controllers using a 1755-HSC module
Counter/Decoder Modes The counters can be used in these operating modes:
•
Counter mode
•
Decoder mode
The two counters can be used in different modes at the same time.
Counter Mode
Counter mode is used for counting pulses at speeds up to 1 MHz on
the GuardPLC 2000 controllers and 100 kHz on the GuardPLC 1200
and 1800 controllers.
Follow these guidelines when using counters in a GuardPLC system:
•
The 5V signal must be between 4.5V and 5.5V, while the 24V
signal must be between 13V and 26.4V.
•
The steepness of the falling edge must be at least 1V per
μ
s.
•
The low and high signal times must be at least 5
μ
s for the
GuardPLC 1200 controller (duty cycle 50% at 100 kHz) and
0.5
μ
s for the GuardPLC 2000 controller (duty cycle 50% at
1 MHz).
•
Shield the cable against noise.
Topic Page
Counter/Decoder Modes 107
Understand Counter Module Configuration 109