BU91530KVT-M Datasheet, PDF (31/60 Pages) Rohm – Multi-function LCD Segment Drivers

BU91530KVT-M
Key Scan Operation Function
1. Key scan timing
The key scan period is 4608T(s). To reliably determine the on/off state of the keys, the BU91530KVT-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 BU91530KVT-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
921⁹6²T¹⁶[S^T[]^S]
T=
1
fosc
Figure 17. Key Scan Timing^(Note22)
(Note22) 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 BU91530KVT-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 BU91530KVT-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]
SCCEE
Serial data transfer Serial data transfer _{Key address(43H)}
SDDI _I
Serial data transfer
9840T[S]
Key address
Key address
SDDO0
Key data read
Key data read request
Key data read
Key data read request
Figure 18. Key Scan Operation in Normal Mode
Key data read
Key data read request
1
T= _fosc
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