3. Key Scan during Sleep Mode

• The pins KS1 to KS6 are set high or low according to the S0 and S1 control data bits.

(See the description of the control data function for details.)

• If a key for a line corresponding to one of the pins KS1 to KS6 which is high is pressed, the oscillator at the OSC

pin starts and a key scan is performed. The key scan continues until all keys have been released. Multiple key

presses can be recognized by determining if multiple key data bits have been set.

• When a key has been pressed for 800T [s] (where T = 1/f

is output to the controller. The controller acknowledges this request and reads the key data. However, DO will go

high when CE is high during a serial data transfer.

• After the controller has finished reading the key data, the LSI clears the key data read request (by setting DO high)

and performs another key scan. Note that since DO is an open drain output, a pull-up resistor of between 1 and 10 k

Ω

is required.

• Key scan example in sleep mode

Example: Here S0 = 0 and S1 = 1 (This is a sleep in which only KS6 is high.)

Multiple Key Presses

Without the insertion of additional diodes, the LC75852 supports key scan for double key presses in general, triple key

presses of keys on the lines for input pins KI1 to KI5, and multiple key presses of keys on the lines for the output pins

KS1 to KS6. However, if multiple key presses in excess of these limits occur, the LC75852 may recognize keys that

were not pressed as having been pressed. Therefore, series diodes must be connected to each key.

No. 4828-10/16

LC75852E, 75852W