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FX3G/FX3U/FX3UC Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
13 High Speed Processing – FNC 50 to FNC 59
13.2 FNC 51 – REFF / Refresh and Filter Adjust
13.2.1 What should be understood before using REFF instruction
Generally, a C-R filter of approximately 10 ms is provided for inputs in PLCs as countermeasures against chattering
and noise at the input contacts.
A digital filter is provided for the inputs X000 to X017
*1
in FX3UC PLCs. The digital filter value can be changed within
the range from 0 to 60 ms using applied instructions.
*1. X000 to X007 in the FX
3U-16M, FX3UC-16M.
1. How to change the digital filter (executing END instruction)
The input filter initial value (10 ms) for X000 to X017
*2
is set in special data register D8020.
By changing this value using the MOV instruction, etc., the input filter value for X000 to X017
*2
which is used during
execution of the END instruction can be changed.
*2. X000 to X007 in the FX
3U-16M, FX3UC-16M.
2. Instruction in which the digital filter is automatically changed
Regardless of the change in the filter time executed by the REFF instruction, when the following functions and
instruction are executed, the input filter value is automatically changed (to 5 µs in X000 to X005 and 50 µs in X006 and
X007).
However, if the digital filter is used in any other functions or instructions than the ones listed, the digital filter uses the
time set in D8020. As a result, the program will not run correctly if the ON or OFF duration of the corresponding input
signal is less than the input filter time.
• Input of interrupt pointer specified in the input interrupt function
• Input used in a high speed counter
• Input used in the SPD (FNC 56) instruction
D8020
REFF
instruction
When the
command is ON
When the END
instruction is
executed
X000 to X017
Input terminal
Digital filter
Initial value: 10 ms
Input image
memory
X020 and
later
Input terminal
C-R filter
Fixed to 10 ms
*2