W90P710_05 Datasheet, PDF (493/526 Pages) Winbond – 16/32-bit ARM microcontroller

W90P710
Continued
BITS
[18]
[17:16]
[15:8]
[7:0]
ENKP
KSIZE
DBTC
PRESCALE
DESCRIPTION
Key pad scan enable
Setting this bit high enable the key scan function.
1 = enable key pad scan
0 = disable key pad scan
Key array size
KSIZE Key array size
2’b00
4x8, 3x8, 2x8, 1x8
2’b01
8x8, 7x8, 6x8, 5x8
2’b1x
16x8, 15x8, 14x8, 13x8, 12x8, 11x8, 10x8, 9x8
Debounce terminal count
Debounce counter counts the number of consecutive scans that
decoded the same keys. When de-bounce counter counter is equal
to terminal count it will generate a key scan interrupt.
Row scan cycle pre-scale value
This value is used to prescale row scan cycle. The prescale counter
is clocked by 0.9375MHz clock.
Key array scan time = 1.067us x PRESCALE x16 ROWS
The following example is the scan time for PRESCALE = 0xFA
Tscan_time = 1.067us x 250 x16 = 4.268ms
If debounce terminal count = 0x05, key detection interrupt is fired in
approximately 21.34ms. The array scan time can range from
17.07us to 1.118 sec.
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Publication Release Date: January 17, 2005
Revision A.2