PT6553_10 Datasheet, PDF (17/41 Pages) Princeton Technology Corp – LCD Driver IC with Key Input Function

LCD Driver IC with Key Input Function
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PT6553
SLEEP MODE
Under the Sleep Mode, the pins -- KO1 to KO6 are set to "HIGH" or "LOW" depending on the states of
the S0 and S1 control data bits. When a key located in one of the lines connected to any of the KO1 to
KO6 pins which is set to "HIGH" is pressed, the oscillation starts and a key scan operation is performed.
Keys are scanned until all the keys are released. Multiple key operation is valid if the multiple key data
bits are set. When a key is pressed longer than 615T (s), PT6553 outputs a key data
request to the controller. The controller acknowledges this request and performs the key data read
operation. However, of CE is set to "HIGH" during the serial data transfer, DO will be set to "HIGH".
After completion of the key data read operation by the controller, the key data read request is cleared
(DO is set to "HIGH") and another key scan operation is performed. Please note that this does not clear
the Sleep Mode. Please also be aware the DO is an open-drain output and requires 1K to 10 KΩ
pull-up resistor. The following is an example of a Sleep Mode Key Scan.
Example: S0="0", S1="1", Sleep Mode with KO6 = "HIGH"
˜L™ KO1
˜L™ KO2
˜L™ KO3
˜L™ KO4
˜L™ KO5
˜H™ KO6
KI1
KI2
KI3
KI4
KI5
When any one of these keys is pressed,
the oscillator starts and the key scan
operation commences.
*
Note: * = It is recommended that these diodes be connected in order to prevent incorrect operation due
to sneak currents in the KO6 scan output signals when the keys on the KO1 to KO5 lines are pressed
simultaneously. These diodes are needed to recognize multiple key presses on the KO6 line under the
sleep mode state with only the KO6 Line is "HIGH" (i.e. the example above.)
PT6553 V1.7
- 17 -
November, 2007