96
The number of times any particular bit can be assigned to conditions is not
limited, so use them as many times as required to simplify your program.
Often, complicated programs are the result of attempts to reduce the number
of times a bit is used.
Except for instructions for which conditions are not allowed (e.g., INTER-
LOCK 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 instruction 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.
Instruction
25313
Instruction
Diagram A
Diagram B
Address
Instruction
Operands
00000
LD
25313
00001
Instruction
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
second 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
5-5-2
AND LOAD and
OR LOAD
for more details and
7-5 Inputting, Modifying and Checking the
Program
for further examples.
00000
00001 00207
00207
00001
00000
00207
00207
Diagram A
Diagram B
Address
Instruction
Operands
00000
LD
00000
00001
LD
00001
00002
AND
00207
00003
OR LD
---
00004
OUT
00207
Address
Instruction
Operands
00000
LD
00001
00001
AND
00207
00002
OR
00000
00003
OUT
00207
Programming Precautions
Section 4-9
Содержание SYSMAC C1000H
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