LC75884E Datasheet, PDF (14/27 Pages) Sanyo Semicon Device – 1/4 Duty LCD Display Drivers with Key Input Function

LC75884E, LC75884W
Key Scan Operation Functions
1. Key scan timing
The key scan period is 384T(s). To reliably determine the on/off state of the keys, the LC75884E/W scans the keys
twice and determines that a key has been pressed when the key data agrees. It outputs a key data read request (a low
level on DO) 800T(s) after starting a key scan. If the key data dose not agree and a key was pressed at that point, it
scans the keys again. Thus the LC75884E/W cannot detect a key press shorter than 800T(s).
Note: *3.In sleep mode the high/low state of these pins is determined by the S0 and S1 bits in the control data. Key scan output signals are not output from
pins that are set low.
2. In normal mode
• The pins KS1 to KS6 are set high.
• 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.
• 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. Also note that DO, being an open-drain output, requires a pull-up resistor (between 1
and 10 kΩ).
No. 6086-14/27