Omron SYSMAC C200HS Operation Manual page 123

Programming Precautions
Diagram A: Incorrect
25313
00000
00001 00207
00001 00207
00000
Except for instructions for which conditions are not allowed (e.g., INTERLOCK
CLEAR and JUMP END, see below), every instruction line must also have at
least one condition on it to determine the execution condition for the instruction
at the right. Again, diagram A , below, must be drawn as diagram B. If an instruc-
tion must be continuously executed (e.g., if an output must always be kept ON
while the program is being executed), the Always ON Flag (SR 25313) in the SR
area can be used.
Diagram B
There are a few exceptions to this rule, including the INTERLOCK CLEAR,
JUMP END, and step instructions. Each of these instructions is used as the sec-
ond of a pair of instructions and is controlled by the execution condition of the
first of the pair. Conditions should not be placed on the instruction lines leading to
these instructions. Refer to Section 5 Instruction Set for details.
When drawing ladder diagrams, it is important to keep in mind the number of
instructions that will be required to input it. In diagram A, below, an OR LOAD
instruction will be required to combine the top and bottom instruction lines. This
can be avoided by redrawing as shown in diagram B so that no AND LOAD or OR
LOAD instructions are required. Refer to 5-8-2 AND LOAD and OR LOAD for
more details and Section 7 Program Monitoring and Execution for further exam-
ples.
Diagram A
Diagram B
Instruction
Address Instruction
Instruction
00000 LD
00001 Instruction
Address Instruction
00207
00000
00001
00002
00003
00004
Address Instruction
00207 00000
00001
00002
00003
Section 4-10
Operands
25313
Operands
LD 00000
LD 00001
AND 00207
OR LD
OUT 00207
Operands
LD 00001
AND 00207
OR 00000
OUT 002
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