LC75808W(2010) View Datasheet(PDF) - SANYO -> Panasonic
Part Name
Description
Manufacturer
LC75808W Datasheet PDF : 38 Pages
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LC75808W
3. In sleep mode
• 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, 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.
1
• If a key is pressed for longer than 800T(s)(where T= fOSC ) the LC75808W 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 LC75808W
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 kΩ and 10 kΩ).
• Sleep mode key scan example
Example: When the control data bits KC1 to KC5 are 0, KC6 is 1, and SP is 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,
the oscillator on the OSC pin is started
and the keys are scanned.
A12913
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
CE
DI
800T [s]
Serial data
transfer
Serial data
transfer
800T [s]
Key address(43H)
Serial data
transfer
Key address
T=
1
fosc
DO
Key data read request
Key data read
Key data read
Key data read request
A12914
Multiple Key Presses
Although the LC75808W 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.6370-23/38
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