lc75808e Sanyo Semiconductor Corporation, lc75808e Datasheet - Page 23

• Manufacturer Part Number: lc75808e
• Description: 1/8 To 1/10 Duty Lcd Display Drivers With Key Input Function
• Manufacturer: Sanyo Semiconductor Corporation

Key Scan Operation Functions
1. Key scan timing
2. In normal mode
Note: *3. Note that the high/low states of these pins are determined by the KC1 to KC6 bits in the control data, and that key scan output signals are not
The key scan period is 384T(s). To reliably determine the on/off state of the keys, the LC75808E/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 LC75808E/W cannot detect a key press shorter than 800T(s).
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The pins KS1 to KS6 are set to high or low by the KC1 to KC6 bits in the control data.
If a key on one of the lines corresponding to a KS1 to KS6 pin which is set high 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=
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 LC75808E/W
performs another key scan. Also note that DO, being an open-drain output, requires a pull-up resistor (between
1 kΩ and 10 kΩ).
output from pins that are set to low.
*3
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LC75808E, 75808W
——
fosc
1
) the LC75808E/W outputs a key data read request (a
*3
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