lc75853nw Sanyo Semiconductor Corporation, lc75853nw Datasheet - Page 22

• Manufacturer Part Number: lc75853nw
• Description: 1/3 Duty Lcd Display Drivers With Key Input Function
• Manufacturer: Sanyo Semiconductor Corporation

Notes on the controller key data read techniques
1. Timer based key data acquisition
• Flowchart
• Timing chart
• Explanation
t3: Key scan execution time when the key data agreed for two key scans. (615 T (s))
t4: Key scan execution time when the key data did not agree for two key scans and the key scan was executed again. (1230 T (s))
t5: Key address (43H) transfer time
t6: Key data read time
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 t7 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 t7 in this technique must satisfy the following condition.
t7 > (t5 + t6 + t4)
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.
T =
Key input
Key scan
f
OSC
1
Controller determination
(key on)
Key data read request
Key
address
Key data read
Key data read
Controller determination
processing
(key on)
LC75853NE, 75853NW
Controller determination
(key off)
Controller determination
(key on)
Controller determination
(key off)
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