LC75884E Datasheet, PDF (15/27 Pages) Sanyo Semicon Device – 1/4 Duty LCD Display Drivers with Key Input Function

LC75884E, LC75884W
3. In sleep mode
• The pins KS1 to KS6 are set to high or low by the S0 and S1 bits in the control data. (See the control data
description for details.)
• 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 pin is started 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.
• If a key is pressed for longer than 800T(s)(Where T= ^{—fo1—sc} ) the LC75884E/W 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.
• After the controller reads the key data, the key data read request is cleared (DO is set high) and the LC75884E/W
performs another key scan. However, this dose not clear sleep mode. Also note that DO, being an open-drain
output, requires a pull-up resistor (between 1 and 10 kΩ).
• Sleep mode key scan example
Example: S0=0, S1=1 (sleep with only KS6 high)
Note: *4.These diodes are required to reliable 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.
Multiple Key Presses
Although the LC75884E/W is capable of key scanning without inserting diodes for dual key presses, triple key presses on
the KI1 to KI5 input pin lines, or multiple key presses on the KS1 to KS6 output pin lines, multiple presses other than
these cases may result in keys that were not pressed recognized as having been pressed. Therefore, a diode must be
inserted in series with each key. Applications that do not recognize multiple key presses of three or more keys should
check the key data for three or more 1 bits and ignore such data.
No. 6086-15/27