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
0004
0000
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