Omron C200HX Operation Manual page 97

Basic Ladder Diagrams
OR and OR NOT
Combining AND and OR
Instructions
When two or more conditions lie on separate instruction lines which run in paral-
lel and then join together, the first condition corresponds to a LOAD or LOAD
NOT instruction; the other conditions correspond to OR or OR NOT instructions.
The following example shows three conditions which correspond (in order from
the top) to a LOAD NOT, an OR NOT, and an OR instruction. Again, each of
these instructions requires one line of mnemonic code.
LR 0000
Address Instruction
00000 LD NOT
00001 OR NOT
00002 OR
00003 Instruction
The instruction will have an ON execution condition when any one of the three
conditions is ON, i.e., when IR 00000 is OFF, when IR 00100 is OFF, or when LR
0000 is ON.
OR and OR NOT instructions can be considered individually, each taking 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 will be
produced for the next instruction.
When AND and OR instructions are combined in more complicated diagrams,
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. Study this example until you are convinced that
the mnemonic code follows the same logic flow as the ladder diagram.
00000 00001 00002
00200
Address
00000
00001
00002
00003
00004
00005
Here, an AND is taken between the status of IR 00000 and that of IR 00001 to
determine the execution condition for an OR with the status of IR 00200. The
result of this operation determines the execution condition for an AND with the
status of IR 00002, which in turn determines the execution condition for an AND
with the inverse (i.e., and AND NOT) of the status of IR 00003.
In more complicated diagrams, however, it is necessary to consider logic blocks
before an execution condition can be determined for the final instruction, and
that's where AND LOAD and OR LOAD instructions are used. Before we consid-
er more complicated diagrams, however, we'll look at the instructions required to
complete a simple "input-output" program.
00000
00100
Operands
00000
00100
LR 0000
00003
Instruction Operands
LD
AND
OR
AND
AND NOT
Instruction
Section 4-4
Instruction
Instruction
00000
00001
00200
00002
00003
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