FX Series Programmable Controlers Applied Instructions 5
5-69
5.6.2 REFF (FNC 51)
Operation:
PLC’s are provided with input filters to overcome
problems generated by mechanical switch gear.
However, as this involves ensuring a steady input
signal is received for a fixed time duration, the use of
input filters slows down the PLC response times. For high speed applications, especially where
solid state switching provides the input signal, input filter times may be reduced. The default
setting for the input filters is approximately 10 msec. Using this instruction input filter times of 0
to 60 msec may be selected. The setting ‘0’ (zero) is actually 50 µsec. This is the minimum
available setting. It is automatically selected when direct input, interrupts or high speed counting
functions are used. The REFF instruction needs to be driven for each program scan if it is to be
effective, otherwise, the standard 10 msec filter time is used.
Mnemonic Function
Operands
Program steps
n
REFF
FNC 51
(Refresh
and filter
adjust)
Inputs are
refreshed, and
their input filters
are reset to the
newly designated
value
K, H,
)
Note: n= 0 to 60 msec (0 = 50µs)
X000 to X007 (X000 to X017 for FX2N)are
automatically designated when using this
instruction
REFF,
REFFP:
3steps
FX
1S
FX
1N
FX
2N
FX
2NC
PULSE-P
16 BIT OPERATION
32 BIT OPERATION
X10
K 1
REFF
[ n ]
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