Rockwell Automation 1772-L8_LW_LWP_LX_LXP,D17726.5.8 User Manual - Manual (Page 348)

Chapter
22
22-1
Selectable Timed Interrupt
This chapter describes a method to execute subroutines at timed intervals.
This method is called selectable timed interrupt (STI).
A selectable timed interrupt is a special subroutine that can be programmed
into the subroutine area and can be executed at timed intervals.
General programming facts are:
The first instruction in the first rung of the subroutine area must be a
Get instruction. This identifies it as an STI.
The Get instruction must be used solely for the purpose of designating
the time period of the STI.
The STI subroutine execution time should not exceed approximately 2/3
STI interval.
Keystrokes: To program a selectable timed interrupt subroutine, a Get
instruction must be the first instruction in the first rung after the use
program subroutine area statement (Figure 22.1). This designates that an
STI follows. Then, you can program your subroutine. The transition time
from main program to STI and return is 100
µ
s.
Chapter Objectives
Introduction