LC75886PW Datasheet, PDF (18/36 Pages) ON Semiconductor – 1/4 and 1/3-Duty LCD Display Driver

LC75886PW
2. Normal mode, when key scan operations are enabled
(1) The KS1 to KS6 pins are set high. (See the description of the control data.)
(2) When a key is pressed, a key scan is started and the keys are scanned until all keys are released. Multiple key
presses are recognized by determining whether multiple key data bits are set.
(3) If a key is pressed for longer than 615T[s] (Where T=1/fOSC or T=1/fCK), the LC75886PW outputs a key data read
request (a low level on DO) to the controller. The controller acknowledges this request and reads the key data.
However, if CE is high during a serial data transfer, DO will be set high.
(4) After the controller reads the key data, the key data read request is cleared (DO is set high) and the LC75886PW
performs another key scan. Also note that DO, being an open-drain output, requires a pull-up resistor (between 1 and
10kΩ).
Key input 1
Key input 2
Key scan
CE
DI
615T[s]
Serial data transfer Serial data transfer
(KSC=0)
(KSC=0)
615T[s]
Key
address(43H)
Serial data transfer
(KSC=0)
615T[s]
Key
address(43H)
Key
address(43H)
DO
Key data read
Key data read
Key data read
Key data read request
Key data read request
Key data read request
3. Sleep mode, when key scan operations are enabled
1
1
T= _fOSC = _fCK
(1) The KS1 to KS6 pins are set to high or low level by the S0 and S1 bits in the control data.
(See the description of the control data.)
(2) If a key on one of the lines corresponding to a KS1 to KS6 pin which is set high is pressed, the oscillator on the OSC
pins starts in RC oscillator operating mode (the IC starts accepting the external clock signal in external clock
operating mode) and a key scan is performed. Keys are scanned until all keys are released.
Multiple key presses are recognized by determining whether multiple key data bits are set.
(3) If a key is pressed for longer than 615T[s] (Where T=1/fOSC or T=1/fCK), the LC75886PW outputs a key data read
request (a low level on DO) to the controller. The controller acknowledges this request and reads the key data.
However, if CE is high during a serial data transfer, DO will be set high.
(4) After the controller reads the key data, the key data read request is cleared (DO is set high) and the
LC75886PW performs another key scan. However, this does not clear sleep mode. Also note that DO, being an
open-drain output, requires a pull-up resistor (between 1 and 10kΩ).
(5) Sleep mode key scan example
Example: S0=0, S1=1 (Sleep with only KS6 high)
“L” KS1
“L” KS2
“L” KS3
“L” KS4
“L” KS5
“H” KS6
*4
KI1
KI2
KI3
KI4
KI5
When any one of these keys is pressed, the
oscillator on the OSC pins starts in RC oscillator
operating mode (the IC starts accepting the external
clock signal in external clock operating mode) and a
key scan operation is performed.
Note: *4. These diodes are required to reliably recognize multiple key presses on the KS6 line when sleep mode state
with only KS6 high, as in the above example. That is, these diodes prevent incorrect operations due to sneak
currents in the KS6 key scan output signal when keys on the KS1 to KS5 lines are pressed at the same time.
No.A1391-18/36