Rockwell Automation 1747-PT1, D1747NP002 Hand-Held Terminal - Manual (Page 427)

Interrupts – 5/02 Processor Only
Chapter 30
Understanding Selectable Timed
30–7
STD/STE Zone Example
In the program below, the STI function is in effect. The STD and STE
instructions in rungs 6 and 12 are included in the ladder program to avoid
having STI subroutine execution at any point in rungs 7 thru 11.
The STD instruction (rung 6) resets the STI enable bit and the STE
instruction (rung 12) sets the enable bit again. The STI timer increments and
may time out in the STD zone, setting the pending bit S:2/0 and overrun bit
S:5/10.
The first pass bit S:1/15 and the STE instruction in rung 0 are included to
insure that the STI function is initialized following a power cycle. You
should include this rung any time your program contains an STD/STE zone
or an STD instruction.
] [
S:1
15
( )
STI interrupt
execution will
not occur
between STD
and STE.
END
0
STD
SELECTABLE TIMED DISABLE
STE
SELECTABLE TIMED ENABLE
] [ ] [
( ) ] [ ] [
( ) ] [ ] [
STE
SELECTABLE TIMED ENABLE
( ) ] [ ] [
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Program File 2