LC75857E Datasheet, PDF (19/39 Pages) Sanyo Semicon Device – CMOS IC 1/3, 1/4 Duty LCD Display Drivers with Key Input Function

LC75857E, LC75857W
3. Sleep mode, when key scan operations are enabled
• The KS1 to KS6 pins are set to the high or low level by the KC0 to KC2 bits in the control data. (See the
description of the control data.)
• When any key on the lines corresponding to KS1 to KS6 pin which is set high is pressed, either the OSC pin
oscillator starts (if the IC is in RC oscillator mode) or the IC starts accepting the external clock signal (if the IC is
in external clock mode), a key scan is performed. Keys are scanned until all keys are released. Multiple key
presses are recoghized by determinig whether multiple key data bits are set.
•
If a key
request
is
(a
pressed for longer than 615T(s)(Where
low level on DO) to the controller. The
Tco=n—tfroo1—slcler=a—cf_{Ck1—Know) ltehdegLeCs t7h5i8s5r7eqEu/Westoauntdpuretsadasktehye}
data
key
read
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 LC75857E/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: KC0 = 1, KC1 = 0, KC2 = 1, (sleep with only KS6 high)
[L] KS1
[L] KS2
[L] KS3
[L] KS4
[L] KS5
[H] KS6
*4
KI1
KI2
KI3
KI4
KI5
When any one of these keys is pressed, either the
OSC pin oscillator starts (if the IC is in RC
oscillator mode) or the IC starts accepting the
external clock signal (if the IC is in external clock
mode) and a key scan operation is performed.
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.
Key input
(KS6 line)
Key scan
615T[s]
CE
Serial data transfer
(KSC = 0)
DI
Serial data transfer
(KSC = 0)
615T[s]
Serial data transfer
Key address (43H)
(KSC = 0)
Key address
T= ¹ = ¹
fosc fCK
DO
Key data read request
Key data read
Key data read
Key data read request
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