BU97520AKV-M Datasheet, PDF (21/44 Pages) Rohm – AEC-Q100 Qualified

BU97520AKV-M
Datasheet
Key Scan Operation Function
17. Key Scan Timing
The key scan period is 4608T(s). To reliably determine the on/off state of the keys, the BU97520AKV-M scans the keys twice
and determines that a key has been pressed when the key data agrees. It outputs a key data read request (a low level on SDO)
9840T(s) after starting a key scan. If the key data does not agree and a key was pressed at that point, it scans the keys again.
Thus the BU97520AKV-M cannot detect a key press shorter than 9840T(s).
KS1 ^* 1
1
*
KS2 ^*
2
2
*
KS3 ^*
3
3
*
KS4 ^*
4
4
*
KS5 ^*
5
5
*
KS6 ^*
6
6
*
9216T[S]
T=
1
fosc
Figure 13. Key Scan Timing^(Note16)
(Note16) *: In sleep mode the high/low state of these pins is determined by the BU0 to BU2 bits in the control data. Key scan output signals are not output from pins
that are set “L”.
2. In Normal Mode
The pins KS1 to KS6 are set “H”.
When a key is pressed a key scan is started and the 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 BU97520AKV-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 “H”.
After the controller reads the key data, the key data read request is cleared (SDO is set high) and the BU97520AKV-M performs
another key scan. Also note that SDO, being an open-drain output, requires a pull-up resistor (between 1 KΩ and 10KΩ).
Key Input 1
Key Input 2
Key scan
9840T[S]
9840T[S]
SCE
Serial data transfer Serial data transfer _{Key address(43H)}
SDI
Serial data transfer
9840T[S]
Key address
Key address
SDO
Key data read request
Key data read
Key data read
Key data read request
Key data read
Key data read request
Figure 14. Key Scan Operation In Normal Mode
1
T= _fosc
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