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Sequence Control Instructions Section 3-4
Differences between
Interlocks and Multiple
Interlocks
Regular interlocks (IL(002) and IL(003)) cannot be nested, but multiple inter-
locks (MILH(517), MILR(518), and MILC(519)) can be nested. Ladder pro-
gramming can be simplified by nesting multiple interlocks, as shown in the
following diagram.
Differences between
MILH(517) and MILR(518)
Differentiated instructions (DIFU, DIFD, or instructions with a @ or % prefix)
operate differently in interlocks created with MILH(517) and MILR(518).
The operation of differentiated instructions in an interlock created with
MILH(517) is identical to the operation in an interlock created with IL(002).
For details, refer to 3-4-5 MULTI-INTERLOCK DIFFERENTIATION HOLD,
MULTI-INTERLOCK DIFFERENTIATION RELEASE, and MULTI-INTER-
LOCK CLEAR: MILH(517), MILR(518), and MILC(519).
Precautions Do not combine interlocks created with different interlock instructions (IL-ILC,
MILH-MILC, and MILR-MILC). The interlocks may not operate properly if dif-
ferent interlock methods are used together. For details on combining instruc-
tions, refer to 3-4-5 MULTI-INTERLOCK DIFFERENTIATION HOLD, MULTI-
INTERLOCK DIFFERENTIATION RELEASE, and MULTI-INTERLOCK
CLEAR: MILH(517), MILR(518), and MILC(519).
a
MILH
0
A1
b
MILH
1
A2
c
MILH
2
A3
MILC
2
MILC
1
MILC
0
a
IL
A1
ILC
a
IL
A2
b
bc
ILC
a
IL
A3
ILC
Interlocks with MILH and MILC Interlocks with IL and ILC
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