Mitsubishi Electronics FX2N ユーザーズマニュアル
FX Series Programmable Controlers
Applied Instructions 5
5-13
5.1.7
FOR, NEXT
(FNC 08, 09)
(FNC 08, 09)
Operation:
T h e F O R a n d N E X T i n s t r u c t i o n s a l l o w t h e
specification of an area of program, i.e. the program
enclosed by the instructions, which is to be repeated
S number of times.
specification of an area of program, i.e. the program
enclosed by the instructions, which is to be repeated
S number of times.
Points to note:
a) The FOR instruction operates in a 16 bit mode hence, the value of the operand S may be
within the range of 1 to 32,767. If a number between the range -32,768 and 0 (zero) is
specified it is automatically replaced by the value 1, i.e. the FOR-NEXT loop would execute
once.
specified it is automatically replaced by the value 1, i.e. the FOR-NEXT loop would execute
once.
b) The NEXT instruction has NO operand.
c) The FOR-NEXT instructions must be programmed as a pair e.g. for every FOR instruction
there MUST be an associated NEXT instruction. The same applies to the NEXT
instructions, there MUST be an associated FOR instruction. The FOR-NEXT instructions
must also be programmed in the correct order. This means that programming a loop as a
NEXT-FOR (the paired NEXT instruction proceeds the associated FOR instruction) is NOT
allowed.
Inserting an FEND instruction between the FOR-NEXT instructions, i.e. FOR-FEND- NEXT,
is NOT allowed. This would have the same effect as programming a FOR without a NEXT
instruction, followed by the FEND instruction and a loop with a NEXT and no associated
FOR instruction.
instructions, there MUST be an associated FOR instruction. The FOR-NEXT instructions
must also be programmed in the correct order. This means that programming a loop as a
NEXT-FOR (the paired NEXT instruction proceeds the associated FOR instruction) is NOT
allowed.
Inserting an FEND instruction between the FOR-NEXT instructions, i.e. FOR-FEND- NEXT,
is NOT allowed. This would have the same effect as programming a FOR without a NEXT
instruction, followed by the FEND instruction and a loop with a NEXT and no associated
FOR instruction.
d) A FOR-NEXT loop operates for its set number of times before the main program is allowed
to finish the current program scan.
e) When using FOR-NEXT loops care should be taken not the exceed the PLC’s watchdog
timer setting. The use of the WDT instruction and/or increasing the watchdog timer value is
recommended.
recommended.
Mnemonic
Function
Operands
Program steps
S
FOR
FNC 08
(Start of a
FOR-NEXT
loop)
FNC 08
(Start of a
FOR-NEXT
loop)
Identifies the start
position and the
number of
repeats for the
loop
position and the
number of
repeats for the
loop
K, H,
KnX, KnY, KnM, KnS,
T, C, D, V, Z
KnX, KnY, KnM, KnS,
T, C, D, V, Z
FOR:
3 step
3 step
NEXT
FNC 09
(End of a
FOR-NEXT
loop)
FNC 09
(End of a
FOR-NEXT
loop)
Identifies the end
position for the
loop
position for the
loop
N/A
Note:
The FOR-NEXT loop can be nested for 5 lev-
els,
i.e. 5 FOR-NEXT loops are programmed within
each other.
Note:
The FOR-NEXT loop can be nested for 5 lev-
els,
i.e. 5 FOR-NEXT loops are programmed within
each other.
NEXT:
1 step
1 step
FX
0(S)
FX
0N
FX FX
(2C)
FX
2N(C)
FX
(2C)
FX
FX
2N(C)
FX
0N
FX
0(s)
PULSE-P
FX
(2C)
FX
FX
2N(C)
FX
0N
FX
0(s)
16 BIT OPERATION
FX
FX
0N
FX
0(s)
FX
(2C)
FX
2N(C)
32 BIT OPERATION
FOR K1X0
NEXT
[ S ]