Logic Block Instructions - Omron C200H Operation Manual

Basic Ladder Diagrams
4-3-6

Logic Block Instructions

AND LOAD
described later. The END instruction requires no operands and no conditions
can be placed on the same instruction line with it.
00000 00001
Address Instruction
00000 LD
00001 AND NOT
00002 Instruction
00003 END(01)
If there is no END instruction anywhere in the program, the program will not
be executed at all.
Now you have all of the instructions required to write simple input-output pro-
grams. Before we finish with ladder diagram basic and go onto inputting the
program into the PC, let's look at logic block instruction (AND LOAD and OR
LOAD), which are sometimes necessary even with simple diagrams.
Logic block instructions do not correspond to specific conditions on the lad-
der diagram; rather, they describe relationships between logic blocks. The
AND LOAD instruction logically ANDs the execution conditions produced by
two logic blocks. The OR LOAD instruction logically ORs the execution condi-
tions produced by two logic blocks.
Although simple in appearance, the diagram below requires an AND LOAD
instruction.
00000 00002
00001 00003
Address Instruction
00000 LD
00001 OR
00002 LD
00003 OR NOT
00004 AND LD
The two logic blocks are indicated by dotted lines. Studying this example
shows that an ON execution condition will be produced when: either of the
conditions in the left logic block is ON (i.e., when either IR 00000 or IR 00001
is ON), and when either of the conditions in the right logic block is ON (i.e.,
when either IR 00002 is ON or IR 00003 is OFF).
The above ladder diagram cannot, however, be converted to mnemonic code
using AND and OR instructions alone. If an AND between IR 00002 and the
results of an OR between IR 00000 and IR 00001 is attempted, the OR NOT
between IR 00002 and IR 00003 is lost and the OR NOT ends up being an
Instruction
END(01)
Operands
00000
00001
---
Operands
00000
00001
00002
00003
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Section 4-3
Program execution
ends here.
Instruction
51