BU91600FV-M Datasheet, PDF (37/67 Pages) Rohm – Low Duty LCD Segment Driver

BU91600xxx Series MAX 148 Segments (37SEG x 4COM)
Datasheet
3. In Power-saving mode
The pins KS1 to KS5 are set to high or low by the BU0 to BU2 bits in the control data. (See the control data description for
details.)
If a key on one of the lines corresponding to a KS1 to KS5 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 9904T(s)(Where T=1/fosc) the BU91600FV-M/BU91600FUV-M outputs a key data read
request (a low level on SDO) to the controller. The controller acknowledges this request and reads the key data. However, if
SCE is high during a serial data transfer, SDO will be set high.
After the controller reads the key data, the key data read request is cleared (SDO is set high) and the
BU91600FV-M/BU91600FUV-M performs another key scan. However, this does not clear power-saving mode. Also note that
SDO, being an open-drain output, requires a pull-up resistor (between 1 KΩ and 10KΩ).
Power-saving mode key scan example
Example: BU0=0, BU1=0, BU2=1 (only KS5 high level output)
KS1/S23
KS2/S24
KS3/S25
KS4/S26
KS5/S27
(Note)
When any one of these keys is pressed,
the oscillator starts and a keys scan
operation is performed.
Kl1/S32
Kl2/S33
Kl3/S34
Kl4/S35
(Note)
These diodes are required to reliable recognize multiple key presses on the KS5 line when only KS5 is high, as in the above example. That is, these diodes prevent
incorrect operations due to sneak currents in the KS5 key scan output signal when keys on the KS1 to KS5 lines are pressed at the same time.
Key Input
Key scan
9904T[S]
9904T[S]
SCE
Serial data transfer Serial data transfer
SDI
Key address(43H) Serial data transfer
Key address
SDO
Key data read
Key data read request
Key data read
Key data read request
T= ¹
fosc
Figure 21. Key Scan Operation in Power-saving Mode
Multiple Key Presses
Although the BU91600FV-M/BU91600FUV-M is capable of key scanning without inserting diodes for dual key presses, triple key
presses on the KI1 to KI4 input pin lines, or multiple key presses on the KS1 to KS5 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 bit and ignore such data.
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