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3.10 KEYPAD Interface
Figure.3-10-1. KEYPAD Interface
The keypad can be divided into two parts: one is the keypad interface including 4 columns and
5 rows; the other is the key detection block which provides key pressed, key released and
de-bounce mechanisms. Each time the key is pressed or released, i.e. something different in the
4 x 5 matrix, the key detection block senses the change and recognizes if a key has been
pressed or released. Whenever the key status changes and is stable, a KEYPAD IRQ is issued.
The MCU can then read the key(s) pressed directly in KP_HI_KEY, KP_MID_KEY and
KP_LOW_KEY registers. To ensure that the key pressed information is not missed, the status
register in keypad is not read-cleared by APB read command. The status register can only be
changed by the key-pressed detection FSM.
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