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LC75808WS-E

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P39
LC75808W
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22
Serial Data Output
1. When CL is stopped at the low level
2. When CL is stopped at the high level
Note: B0 to B3, A0 to A3…….. CCB address ‘43H’
KD1 to KD30 .................. Key data
SA ................................... Sleep acknowledge data
Note: If a key data read operation is executed when DO is high, the read key data (KD1 to KD30) and sleep
acknowledge data(SA) will be invalid.
Output Data
1. KD1 to KD30: Key data
When a key matrix of up to 30 keys is formed from the KS1 to KS6 output pins and the KI1 to KI5 input pins and
one of those keys is pressed, the key output data corresponding to that key will be set to 1. The table shows the
relationship between those pins and the key data bits.
KI1 KI2 KI3 KI4 KI5
KS1 KD1 KD2 KD3 KD4 KD5
KS2 KD6 KD7 KD8 KD9 KD10
KS3 KD11 KD12 KD13 KD14 KD15
KS4 KD16 KD17 KD18 KD19 KD20
KS5 KD21 KD22 KD23 KD24 KD25
KS6 KD26 KD27 KD28 KD29 KD30
When the states of the KS1 to KS6 output pins during key scan standby are set to low for KS1 and KS2 and to high
for KS3 to KS6 by the KC1 to KC6 bits in the control data and a key matrix of up to 20 keys is formed from the KS3
to KS6 output pins and the KI1 to KI5 input pins, the KD1 to KD10 key data bits will be set to 0.
2. SA: Sleep acknowledge data
This output data bit is set to the state when the key was pressed. Also, while DO will be low in this case, if serial data
is input and the mode is set (to normal or sleep mode) during this period, that mode will be set. SA will be 1 in sleep
mode and 0 in normal mode.
1 0 0 0 0 1 0
X
KD1 KD2 KD27
X : don't care
KD28 KD29 KD30 SA
1
B1 B2 B3 A0 A1 A2 A3B0
CE
CL
DI
DO
Output data
A12909
1 0 0 0 0 1 0
KD1
X
KD2 KD3 KD28
X : don't care
KD29 KD30 SA
X
1
B1 B2 B3 A0 A1 A2 A3B0
CE
CL
DI
DO
Output data
A12910
LC75808W
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Key Scan Operation Functions
1. Key scan timing
The key scan period is 384T(s). To reliably determine the on/off state of the keys, the LC75808W 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 LC75808W cannot detect a key press shorter than 800T(s).
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 output from pins that are set to low.
2. In normal 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, 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= ) 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. Also note that DO, being an open-drain output, requires a pull-up resistor (between 1
k and 10 k).
1
f
OSC
800T [s] 800T [s] 800T [s]
Serial data
transfer
Serial data
transfer
Serial data
transfer
Key address(43H) Key address Key address
Key data read request
Key data read Key data read
Key data read request
Key data read
Key data read request
A12912
Key input 1
Key input 2
Key scan
CE
DI
DO
fosc
1
T=
1 *3*3
KS1
2 *3
*3
KS2
3*3
*3
KS3
4*3
*3
KS4
5
1
2
3
4
5*3
*3
KS5
6
768T [s]
6
A12911
*3*3
KS6
Key on
fosc
1
T=
LC75808W
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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.
If a key is pressed for longer than 800T(s)(where T= ) 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 k and 10 k).
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)
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.
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.
1
f
OSC
800T [s] 800T [s]
Serial data
transfer
Serial data
transfer
Serial data
transfer
Key address(43H) Key address
Key data read request
Key data read Key data read
Key data read request
A12914
Key input
(KS6 line)
Key scan
CE
DI
DO
fosc
1
T=
[L] KS1
[L] KS2
[L] KS3
[L] KS4
[H] KS6
KI1
KI2
KI3
KI4
[L] KS5
KI5
*4
A12913
When any one of these keys is pressed,
the oscillator on the OSC pin is started
and the keys are scanned.
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LC75808WS-E

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Buy LC75808WS-E
Manufacturer:
ON Semiconductor
Description:
LCD Drivers LCD DISPLAY DRIVER
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