• In normal mode

— The pins KS1 to KS6 are set high.

— A key scan is started when any of the keys is pressed, and the keys are kept scanning until all keys are released.

The controller can recognize simultaneous multiple key presses by checking the key data for multiple bits being set.

by setting DO low. The controller acknowledges this state and reads the key data. However, note that DO will go

high when CE is set high during the serial data transfer.

— After the controller key data readout completes, the key data read request will be cleared (DO will be set high), and

the IC performs another key scan. Note that since DO is an open-drain output, a pull-up resistor (between 1 and

10 k

Ω) is required.

• In sleep mode

— The pins KS1 to KS6 are set to high or low according to the values of S0 and S1 in the control data. (See the

description of the control data elsewhere in this document.)

— If a key connected to one of the KS1 to KS6 lines that was set high is pressed, the clock generator (oscillator circuit)

is started and a key scan is performed, and the keys are kept scanning until all keys are released.

The controller can recognize simultaneous multiple key presses by checking the key data for multiple bits being set.

by setting DO low. The controller acknowledges this state and reads the key data. However, note that DO will go

high when CE is set high during the serial data transfer.

— After the controller key data readout completes, the key data read request will be cleared (DO will be set high), and

the IC performs another key scan. However, sleep mode will not be cleared. Note that since DO is an open-drain

output, a pull-up resistor (between 1 and 10 k

Ω) is required.

— Example of a key scan operation in sleep mode

Example: Sleep mode with S0 = 0, S1 = 1 (Only KS6 is set high)

Note *: These diodes are required to reliably recognize multiple key presses on the KS6 line when the IC is set to sleep mode with only KS6 set to high as in

the example above. That is, they prevent incorrect recognition of key presses due to sneak currents arising from simultaneous presses of keys on

the KS1 through KS5 lines.

No. 6142-10/18

LC75742E, LC75742W

If one of these keys is pressed, clock

generator (oscillator circuit) is started and

a key scan is performed.

Serial data transfer

Key input 1

Key input 2

Key scan

Serial data transfer

Serial data transfer

Key data read

Key data read request

Key data read

Key data read request

Key data read

Key data read request

Key address (8FH)

Key address

Key address