Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 208)

Preface MicroLogix 1000 Programmable Controllers User Manual
11–20
Selectable Timed Start (STS)
Use the STS instruction to condition the start of the STI timer upon entering the
REM Run mode – rather than starting automatically. You can also use it to set up or
change setpoint/frequency of the STI routine that will be executed when the STI
timer expires.
This instruction is not required to configure a basic STI interrupt application.
The STS instruction requires you to enter the parameter for the STI setpoint. Upon
a true execution of the rung, this instruction enters the setpoint in the status file
(S:30), overwriting the existing data. At the same time, the STI timer is reset and
begins timing; at timeout, the STI subroutine execution occurs. When the rung goes
false, the STI function remains enabled at the setpoint you’ve entered in the STS
instruction.
Interrupt Subroutine (INT)
This instruction serves as a label or identifier of a program file as an interrupt
subroutine (INT label) versus a regular subroutine (SBR label).
This instruction has no control bits and is always evaluated as true. The instruction
must be programmed as the first instruction of the first rung of the subroutine. Use
of this instruction is optional; however, we recommend using it.
Execution Times
(
µ
sec) when:
True False
24.59 6.78
STS
SELECTABLE TIMED START
File
Time [x 10ms]
Execution Times
(
µ
sec) when:
True False
1.45 0.99
INTERRUPT SUBROUTINE
INT