LC75817E Datasheet, PDF (23/43 Pages) Sanyo Semicon Device – 1/8 to 1/10 Duty Dot Matrix LCD Display Controller/Driver with Key Input Function

LC75817E, 75817W
• In sleep mode
• _{The pins KS1 to KS6 are set to high or low with the “set key scan output state” instruction.}
• _{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}
OSCI, OSCO pins 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.
• _{If a key is pressed for longer than 4800T(s)(Where T= —fo}¹_{—sc ) the LC75817E/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 LC75817E/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: When a “display on/off control (SP = 1)” instruction and a “set key scan output state (KC1 to KC5 = 0,
KC6 = 1)” instruction are executed (i.e. sleep mode with only KS6 high)
“L” KS1
“L” KS2
“L” KS3
“L” KS4
“L” KS5
“H” KS6
KI1
KI2
KI3
KI4
KI5
When any one of these keys is pressed, the oscillator on the
OSCI, OSCO pins is started and the keys are scanned.
*19
Note: *19. These diodes are required to reliably 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
4800T(s)
Serial data
transfer
Serial data
transfer
Key address
(43H)
4800T(s)
Serial data
transfer
Key address
T= ¹
fosc
DO
Key data read request
Key data read
Key data read
Key data read request
Multiple Key Presses
Although the LC75817E/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.
No. 6144-23/43