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LC75808W-SH-E

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P39
LC75808W
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37
Notes on the Controller Key Data Read Techniques
1. Timer based key data acquisition
Flowchart
Timing chart
Explanation
In this technique, the controller uses a timer to determine key on/off states and read the key data. The controller must
check the DO state when CE is low every t9 period without fail. If DO is low, the controller recognizes that a key has
been pressed and executes the key data read operation.
The period t9 in this technique must satisfy the following condition.
t9 > t6 + t7 + t8
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.
CE=[L]
Key data
read processing
DO=[L]
NO
YES
A12928
t5:Key scan execution time when the key data agreed for two key scans. (800T(s))
t6:Key scan execution time when the key data did not agree for two key scans and
the key scan was executed again. (1600T(s))
t7:Key address (43H) transfer time
t8:Key data read time
1
f
OSC
T=
t9 t9 t9 t9
t6
t5
t8
t7
t7
t7
t8 t8
t5 t5
Key on Key on
Key input
CE
DI
DO
Key scan
Key
address
Key data read
Key data read request
Controller
detemination
(Key on)
Controller
detemination
(Key on)
Controller
detemination
(Key on)
Controller
detemination
(Key off)
Controller
detemination
(Key off)
A1292
9
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2. Interrupt based key data acquisition
Flowchart
Timing chart
Explanation
In this technique, the controller uses interrupts to determine key on/off states and read the key data. The controller
must check the DO state when CE is low. If DO is low, the controller recognizes that a key has been pressed and
executes the key data read operation. After that the next key on/off determination is performed after the time t10 has
elapsed by checking the DO state when CE is low and reading the key data. The period t10 in this technique must
satisfy the following condition.
t10 > t6
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.
t5: Key scan execution time when the key data agreed for two key scans. (800T(S))
t6: Key scan execution time when the key data did not agree for two key scans and
the key scan was executed again. (1600T(S))
t7: Key address (43H) transfer time
t8: Key data read time
1
f
OSC
T=
t10
t5
t8
t7
Key on
Key input
CE
DI
DO
Key scan
Key
address
Key data read
Key data read request
t10
t6t5
t8
t7
t7
t8
Key on
t10
t5
t8
t7
t10
A
12931
Controller
detemination
(Key on)
Controller
detemination
(Key on)
Controller
detemination
(Key on)
Controller
detemination
(Key on)
Controller
detemination
(Key off)
Controller
detemination
(Key off)
CE=[L]
CE=[L]
Key data
read processing
DO=[L]
DO=[H]
Key OFF
NO
NO
YES
YES
A12930
Wait for at least t10
LC75808W
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39
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ORDERING INFORMATION
Device Package Shipping (Qty / Packing)
LC75808W-E
SPQFP100 14x14 / SQFP100
(Pb-Free / Halogen Free)
300 / Tray Foam
LC75808W-SH-E
SPQFP100 14x14 / SQFP100
(Pb-Free)
60 / Tray Foam
LC75808WS-E
SPQFP100 14x14 / SQFP100
(Pb-Free / Halogen Free)
300 / Tray Foam
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P39

LC75808W-SH-E

Mfr. #:
Buy LC75808W-SH-E
Manufacturer:
ON Semiconductor
Description:
IC LCD DISPLAY DRIVER
Lifecycle:
New from this manufacturer.
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