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4-10 Programming Precautions
The number of conditions that can be used in series or parallel is unlimited as
long as the memory capacity of the PC is not exceeded. Therefore, use as many
conditions as required to draw clear diagrams. Although very complicated dia-
grams can be drawn with instruction lines, there must not be any conditions on
lines running vertically between two other instruction lines. Diagram A shown
below, for example, is not possible, and should be drawn as diagram B. Mne-
monic code is provided for diagram B only; coding diagram A would be impossi-
ble.
Diagram A
Diagram B
Address
Instruction
00000
LD
000001
00001
AND
000004
00002
OR
000000
00003
AND
000002
00004
Instruction 1
00005
LD
000000
00006
AND
000004
00007
OR
000001
00008
AND NOT
000003
00009
Instruction 2
Operands
0000
00
0000
01
0000
02
0000
03
0000
04
0000
01
0000
00
0000
04
0000
02
0000
00
0000
01
0000
04
0000
03
Instruction 1
Instruction 2
Instruction 2
Instruction 1
The number of times any particular bit can be assigned to conditions is not lim-
ited, 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., 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 (A50013) in the Auxil-
iary Area can be used.
Diagram A
Diagram B
Address
Instruction
00000
LD
A50013
00001
Instruction
Operands
Instruction
A500
13
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 se-
cond 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.
Programming Precautions
Section 4-10
Summary of Contents for CVM1D
Page 462: ...SYSMAC CVM1D Duplex System Programmable Controllers Operation Manual Revised August 2001...
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