Allen-Bradley PLC-2/30

Jump Instructions and
Subroutine Programming
Chapter 11
1113
Figure 11.10
(a)
Three Levels of Nested Subroutines
(b) A Subroutine Can Call Itself or Loop
Subroutine
Level
1
Subroutine
Level 2
Subroutine
Level 3
( JSR )
( RET )
( JSR )
( RET ) ( RET )
02 03
( JSR )
01
Main
Program
LBL
01
LBL
02
LBL
03
a
bc
def
Subroutine Area (A.)
LBL ( SCT )
01 051
| / |
15
( JSR )
051 01
PR 999
AC 000
( JSR )
01
Main
Program
Subroutine Area (B.)
( CTR )
051
PR 009
AC 000
( RET )
Y our Subroutine
End XXXXX
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