STMPE2403 datasheet(55/63 Pages) STMICROELECTRONICS

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STMPE2403

Keypad controller

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12.8.4

Priority of Key detection

Dedicated key will always be detected, if it is enabled.

When a Special Function key is detected, the matrix key scanning on the same input line will

be disabled.

Up to 3 matrix keys will be detected. Matrix keys that fall on activated Special Function keys

will not be counted.

As a result of these rules of priority, a matrix key will be ignored by the keypad controller

when the special function key on the same input line is detected, even if the matrix key is

being pressed down before the special function key. Hence, when a matrix is reported “key-

down” and it is being held down while the corresponding special function is being pressed, a

“no-key” status will be reported for the matrix key when the special function key is reported

“key-down”. If the matrix key is released while the special function key is still being held

down, no “key-up” will be reported for the matrix key. On the other hand, if the matrix key is

released after the special function key is reported “key-up”, then a new “key-down” will be

reported for the matrix key, followed by “key-up”.

12.8.5

Keypad Wake-Up from sleep and hibernate modes

The keypad controller is functional in sleep mode as long as it is enabled before entering sleep mode.

It will then wake the system up into operational mode if a valid key press is detected.

In the case of hibernate mode, the ‘Hib_Wk’ bit in ‘KPC_row_msb’ register must be set to ‘1’ in order to

enable system wake-up by valid key press. When this is enabled, asynchronous detection of keypad

column input activity will be turned on during hibernate mode. If any key activity is detected, the

system is expected to enter sleep mode temporarily to allow de-bouncing of key press to take place. If

a valid key is detected, the system will then wake up into operational mode; otherwise, the device will

go back into hibernate mode.

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