Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 260)

Chapter 14
Using High-Speed Counter Instructions
14–10
When a high preset is reached, the:
•
HP bit is set.
•
High-speed counter interrupt file (file 4) is executed if the interrupt is
enabled. The IH bit is set and the IL, IV, and IN bits are reset.
Unlike the Up Counters, the accumulator value is not reset and the high
preset value is not loaded from the image to the hardware high preset
register.
The Following Condition Occurs when
either the hardware accumulator transitions from the
hardware low preset +1 to the hardware low preset, or
A low preset is reached
the hardware accumulator is loaded with a value less than
or equal to the hardware low preset, or
the hardware low preset is loaded with a value that is
greater than or equal to the hardware accumulator.
When the low preset is reached, the:
•
LP bit is set.
•
High-speed counter interrupt file (file 4) is executed if the interrupt is
enabled. The IL bit is set and the IH, IV, and IN bits are reset.
An overflow occurs when the hardware accumulator transitions from
+
32,767 to –32,768. When an overflow occurs, the:
•
OV bit is set.
•
High-speed counter interrupt file (file 4) is executed if the interrupt is
enabled. The IV bit is set and the IH, IL, and IN bits are reset.
An underflow occurs when the hardware accumulator transitions from
–32,768 to
+
32,767. When an underflow occurs, the:
•
UN bit is set.
•
High-speed counter interrupt file (file 4) is executed if the interrupt is
enabled. The IN bit is set and the IH, IL, and IV bits are reset.
The following tables summarize what the input state must be for the
corresponding high-speed counter action to occur:
Bidirectional Counter (Pulse/direction)
Input State High-Speed
Count r Input Count
(I/0)
Input
Direction (I/1)
Input Reset
(I/2)
Input Hold
(I/3)
HSC Rung
High-Speed
Counter
Action
Turning
Off-to-On
Off NA NA True Count Up
Turning
Off-to-On
On NA NA True Count Down
NA NA NA NA False Hold Count
NA (Not Applicable)