Renesas M16C/50 Series User Manual page 200

M16C/5L Group, M16C/56 Group
11.4.3 Digital Debounce Filters
The MCU has two digital debounce filters for noise reduction, assigned to NMI / SD and INT5 /INPC1_7.
Registers NDDR and P17DDR set the filter widths, respectively.
The digital debounce function is triggered by a rising or falling edge of digital input signal to either
NMI / SD and INT5 /INPC1_7. When the input pulse is longer than the filter width set by a program, the
signal level is determined. Any noise that is shorter than the filter width is blocked by this function.
Digital debounce function is disabled to the port P1_7/IDU input and the port P8_5 input.
(n +
Filter width:
-------------------------- -
Registers NDDR and P17DDR decrement the setting value as f1 divided-by-8 is the count source.
When reading the NDDR or P17DDR register, the count value is returned. The setting value is reloaded
at every falling or rising edge of the pin input.
When using the digital debounce function, the programmable value for the NDDR or P17DDR register
is 00h to FFh. When setting FFh to the register, digital debounce filter function is not selected. See
Figure 11.8 for details.
R01UH0127EJ0110 Rev.1.10
Sep 01, 2011
1 ) ×
8
n: the NDDR or P17DDR register setting value
f1
11. Programmable I/O Ports
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