BU97550KV-M Datasheet, PDF (40/72 Pages) Rohm – AEC-Q100 Qualified

BU97550KV-M
Datasheet
3. In Sleep Mode
The pins KS1 to KS6 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 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 9840T(s)(Where T=1/fosc) the BU97550KV-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 BU97550KV-M performs
another key scan. However, this does not clear sleep mode. Also note that SDO, being an open-drain output, requires a pull-up
resistor (between 1 and 10KΩ).
Sleep mode key scan example
Example: BU0=0, BU1=0, BU2=1 (sleep with only KS6 high)
(L)KS1
(L)KS2
(L)KS3
(L)KS4
(L)KS5
(₍H_L)_)KS6
(Note29)
When any one of these keys is pressed,
the oscillator on the OSC pin is started
and the keys are scanned.
Kl1
Kl2
Kl3
Kl4
Kl5
(Note 29)
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.
Key Input 2
(KS6 line)
Key scan
9840T[S]
9840T[S]
SCCEE
Serial data transfer Serial data transfer
S_DD_II
Key address(43H) Serial data transfer
Key address
SD_DO₀
Key data read
Key data read request
Key data read
Key data read request _T=
1
fosc
Figure 23. Key scan operation in sleep mode
Multiple Key Presses
Although the BU97550KV-M 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 bit and ignore such data.
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