Filter
Top Products
12 Applied Instructions (High Speed Processing)
262
FXCPU Structured Programming Manual
[Basic & Applied Instruction]
12.2 REFF / Refresh and Filter Adjust
12.2.1 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 some inputs (*1). The digital filter value can be changed within the range from 0
to 60 ms using instructions.
1. How to change the digital filter (executing END instruction)
The digital filter initial value (10 ms) 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. 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
instructions are executed, the input filter value is automatically changed (as shown in the caution).
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 instruction
REFF instruction
Input terminal
Digital filter
Initial value: 10 ms
*1. Where a digital filter is used on an input terminal, refer to the descriptions
on the functions and operations.
Input image
memory
C-R filter
Fixed to 10 ms
Input terminal
*1
When the
command is ON
When the END
instruction is executed
D8020