Samsung S5PC110 Manual page 1940

S5PC110_UM
8.2 DEBOUNCING FILTER
The debouncing filter is supported for keypad interrupt of any key input. The filtering width is approximately
62.5usec ("FCLK" two-clock, when the FCLK is 32kHz). The keypad interrupt (key pressed or key released) to the
CPU is an ANDed signal of the all row input lines after filtering.
FILTER _ IN
FILTER _OUT
Filter width : FCLK two - clock
Filter Clock ( FCLK ) is a FLT _ CLK or the division of that clock.
FLT _ CLK is come from System Controller, OSC_ IN or USB _ XTI.
Figure 8-2 Internal Debouncing Filter Operation
FCLK two - clock width
8 KEYPAD INTERFACE
8-3