BU91520KV-M Datasheet, PDF (25/45 Pages) Rohm – Low Duty LCD Segment Driver

BU91520KV-M
In this technique, the controller uses interrupts to determine key on/off states and read the key data. The controller must check
the SDO state when SCE is low. If SDO 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 t8 has elapsed by checking the SDO state
when SCE is low and reading the key data. The period t8 in this technique must satisfy t8 > t4.
If a key data read operation is executed when SDO is high, the read key data (KD1 to KD30) and power-saving acknowledge
data
(PA) will be invalid.
Key Input 1
Key scan
Key on
t3
Key on
t3
t4
t3
SCE
SDI
SDO
t6
t5
Key data read
t6
t5
t6
t5
t6
t5
Key data read request
Controller
determination
(key on)
t8
Controller Controller
determination determination
(key on)
(key on)
t8
Controller
determination
(key on)
t8
Controller
determination
(key on)
t8
Controller
determination
(key on)
t3: Key scan execution time when the key data agreed for two key scans. (9840T(s))
t4: Key scan execution time when the key data did not agree for two key scans and the key scan was executed again.
(19680T(s)) T = 1 / fosc
t5: Key address (43H) transfer time
t6: Key data read time
Figure 19. Interrupt Based Key Data Read Operation
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