Rainbow-electronics W90P710CDG Bedienungsanleitung PDF herunterladen (Seite 504)

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W90P710CD/W90P710CDG

Publication Release Date: September 19, 2006

- 505 - Revision B2

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BITS DESCRIPTION

[18] ENKP

Key pad scan enable

Setting this bit high enable the key scan function.

1 = enable key pad scan

0 = disable key pad scan

[17:16] KSIZE

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

[15:8] DBTC

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.

[7:0] PRESCALE

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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