BU91600FV-M Datasheet, PDF (36/67 Pages) Rohm – Low Duty LCD Segment Driver

BU91600xxx Series MAX 148 Segments (37SEG x 4COM)
Datasheet
Key Scan Operation Function
1. Key scan timing
The key scan period is 4640T(s). To reliably determine the on/off state of the keys, the BU91600FV-M/ BU91600FUV-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) 9904T(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 BU91600FV-M/ BU91600FUV-M cannot detect a key press shorter than 9904T(s).
KS1 ^*
1
1
*
KS2 *
2
2
*
KS3 *
3
3
*
KS4 *
4
4
*
KS5 ^*
5
5
*
*
9280T[S]
T= ¹
*
fosc
Figure 19. Key Scan Timing^(Note)
(Note) In power-saving 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 KS5 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 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 “H”.
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. 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
9904T[S]
9904T[S]
SCE
Serial data transfer Serial data transfer _{Key address(43H)}
SDI
Serial data transfer
9904T[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 20. Key Scan Operation in Normal Mode
1
T=
fosc
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