Omron CVM1D, Operation Manual

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4-3-5 The END Instruction
The last instruction required to complete any program is the END instruction.
When the CPU scans a program, it executes all instructions up to the first END
instruction before returning to the beginning of the program and beginning
execution again. Although an END instruction can be placed at any point in a
program, which is sometimes done when debugging, no instructions past the
first END instruction will be executed. The number following the END instruction
in the mnemonic code is its function code, which is used when inputting most
instructions into the PC. Function codes are described in more detail later. The
END instruction requires no operands and no conditions can be placed on the
instruction line with it.
Program
execution
ends here.
Address Instruction
00500 LD 000000
00501 AND NOT 000001
00502 Instruction
00503 END(001) ---
Operands
Instruction
0000
00
0000
01
(001)
END
If there is no END instruction anywhere in a program, the program will not be
executed at all.
4-4 Mnemonic Code
4-4-1 Logic Block Instructions
Logic block instructions do not correspond to specific conditions on the ladder
diagram; rather, they describe relationships between logic blocks. Each logic
block is started with a LOAD or LOAD NOT instruction. Whenever a LOAD or
LOAD NOT instruction is executed, a new execution condition is created and the
previous execution condition is stored in a buffer. The AND LOAD instruction
logically ANDs the execution conditions produced by two logic blocks, i.e., gen-
eral speaking, it ANDs the current execution condition with the last execution
condition stored in a buffer. The OR LOAD instruction logically ORs the execu-
tion conditions produced by two logic blocks.
Although simple in appearance, the diagram below requires an AND LOAD
instruction.
Address Instruction
00000 LD 000000
00001 OR 000001
00002 LD 000002
00003 OR NOT 000003
00004 AND LD ---
0000
00
Instruction
0000
02
0000
01
0000
03
Operands
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 CIO 000000 or CIO 000001 is ON) and
either of the conditions in the right logic block is ON (i.e., when either
CIO 000002 is ON or CIO 000003 is OFF).
AND LOAD
Mnemonic Code
Section 4-4