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When two or more conditions lie on separate instruction lines running in par-
allel and then joining together, the first condition corresponds to a LOAD or
LOAD NOT instruction; the rest of the conditions correspond to OR or OR
NOT instructions. The following example shows three conditions which corre-
spond in order from the top to a LOAD NOT, an OR NOT, and an OR instruc-
tion.
Instruction
0100
HR 000
0000
Address
Instruction
Operands
0000
LD
0000
0001
OR NOT
0100
0002
OR
HR
000
0003
Instruction
The instruction at the right would have an ON execution condition when any
one of the three conditions was ON, i.e., when IR 0000 was OFF, when IR
0100 was OFF, or when HR 000 was ON.
OR and OR NOT instructions can also be considered individually, each tak-
ing the logical OR between its execution condition and the status of the OR
instruction’s operand bit. If either one of these were ON, an ON execution
condition would be produced for the next instruction.
When AND and OR instructions are combined in more complicated dia-
grams, they can sometimes be considered individually, with each instruction
performing a logic operation on the execution condition and the status of the
operand bit. The following is one example.
Instruction
0002
0003
0000
0001
0200
Address
Instruction
Operands
0000
LD
0000
0001
AND
0001
0002
OR
0200
0003
AND
0002
0004
AND NOT
0003
0005
Instruction
Here, an AND is taken between the status of 0000 and that of 0001 to deter-
mine the execution condition for an OR with the status of 0200. The result of
this operation determines the execution condition for an AND with the status
of 0002, which in turn determines the execution condition for an AND with the
inverse of the status of 0003. In more complicated diagrams, however, it is
necessary to consider logic blocks before an execution condition can be de-
termined for the final instruction, and that’s where AND LOAD and OR LOAD
instructions are used.
OR and OR NOT
Combining AND and OR
Instructions
The Ladder Diagram
Section 4-3
Summary of Contents for SYSMAC C20K
Page 1: ...Cat No W146 E1 5 Programmable Controllers SYSMAC C20K C28K C40K C60K ...
Page 2: ...K type Programmable Controllers OPERATION MANUAL Revised July 1999 ...
Page 3: ...iv ...
Page 5: ...vi ...
Page 19: ...7 SECTION 2 Hardware Considerations 2 1 Introduction 2 2 Indicators 2 3 PC Configuration ...