86
(ILC(03)) instructions to eliminate the branching point completely while allow-
ing a specific execution condition to control a group of instructions. The IN-
TERLOCK and INTERLOCK CLEAR instructions are always used together.
When an INTERLOCK instruction is placed before a section of a ladder pro-
gram, the execution condition for the INTERLOCK instruction will control the
execution of all instruction up to the next INTERLOCK CLEAR instruction. If
the execution condition for the INTERLOCK instruction is OFF, all right-hand
instructions through the next INTERLOCK CLEAR instruction will be ex-
ecuted with OFF execution conditions to reset the entire section of the ladder
diagram. The effect that this has on particular instructions is described in 5-8
INTERLOCK and INTERLOCK CLEAR – IL(02) and ILC(03).
Diagram B can also be corrected with an interlock. Here, the conditions lead-
ing up to the branching point are placed on an instruction line for the INTER-
LOCK instruction, all of lines leading from the branching point are written as
separate instruction lines, and another instruction line is added for the IN-
TERLOCK CLEAR instruction. No conditions are allowed on the instruction
line for INTERLOCK CLEAR. Note that neither INTERLOCK nor INTER-
LOCK CLEAR requires an operand.
Instruction 1
00002
00000
Instruction 2
00001
ILC(03)
IL(02)
Address Instruction Operands
00000 LD 00000
00001 IL(02) ---
00002 LD 00001
00003 Instruction 1
00004 LD 00002
00005 Instruction 2
00006 ILC(03) ---
If IR 00000 is ON in the revised version of diagram B, above, the status of IR
00001 and that of IR 00002 would determine the execution conditions for in-
structions 1 and 2, respectively. Because IR 00000 is ON, this would produce
the same results as ANDing the status of each of these bits. If IR 00000 is
OFF, the INTERLOCK instruction would produce an OFF execution condition
for instructions 1 and 2 and then execution would continue with the instruc-
tion line following the INTERLOCK CLEAR instruction.
Inputting, Modifying, and Checking the Program Section 4-6
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