lc75857e Sanyo Semiconductor Corporation, lc75857e Datasheet - Page 20

• Manufacturer Part Number: lc75857e
• Description: 1/3, 1/4 Duty Lcd Display Drivers With Key Input Function
• Manufacturer: Sanyo Semiconductor Corporation

4. Normal/sleep mode, when key scan operations are disabled
Multiple Key Presses
Although the LC75857E/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.
Key input 1
Key input 2
Key scan
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•
•
•
•
The KS1 to KS6 pins are set to the high or low level by the KC0 to KC2 bits in the control data.
No key scan operation is performed, whichever key is pressed.
If the key scan disabled state (KSC = 1 in the control data) is set during a key scan, the key scan is stopped.
If the key scan disabled state (KSC = 1 in the control data) is set when a key data read request (a low level on DO)
is output to the controller, all the key data is set to 0 and the key data read request is cleared (DO is set high).
Note that DO, being an open-drain output, requires a pull-up resister (between 1 to 10 kΩ).
The key scan disabled state is cleared by setting KSC in the control data to 0.
CE
DI
DO
Serial data transfer
(KSC = 0)
Serial data transfer
(KSC = 1)
Serial data transfer
LC75857E, LC75857W
(KSC = 0)
615T[s]
Key data read request
Serial data transfer
(KSC = 1)
Serial data transfer
(KSC = 0)
Key data read request
615T[s]
Key address
T=
No. 7980-20/39
fosc
(43H)
1
=
Key data
f
1
CK
read