69
scan by DIFU(10). Assuming the other conditions controlling bit 0100 are not
keeping it ON, the work bit 0200 will turn bit 0100 ON for one scan only.
0200
DIFU(10) 0200
0000
0001 0002 0003
0004 0005
0100
Address Instruction Operands
000 LD 0000
001 DIFU(10) 0200
002 LD 0200
003 LD 0001
004 AND NOT 0002
005 AND NOT 0003
006 OR LD ---
007 LD 0004
008 AND NOT 0005
009 OR LD ---
010 OUT 0100
3-6-7 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 a clear diagram. Although very compli-
cated diagrams can be drawn with instruction lines, there must not be any
conditions on lines running vertically between two other instruction lines. Dia-
gram A shown below, for example, is not possible, and should be drawn as
diagram B. Mnemonic code is provided for diagram B only; coding diagram A
would be impossible.
Instruction 2
Instruction 1
0002
0003
0000
0001
0004
Diagram A
Instruction 1
0004
0003
0000
0001
Diagram B
0002
Instruction 2
00040000
0001
Address Instruction Operands
000 LD 0001
001 AND 0004
002 OR 0000
003 AND 0002
004 Instruction 1
005 LD 0000
006 AND 0004
007 OR 0001
008 AND NOT 0003
009 Instruction 2
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. Of-
ten, 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, 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 (bit 0408) can be
used.
Advanced Programming Section 3-6
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