LC75804W 查看數據表（PDF） - SANYO -> Panasonic
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LC75804W Datasheet PDF : 37 Pages
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LC75804E, LC75804W
Key Scan Operation Functions
1. Key scan timing
The key scan period is 288T(s). To reliably determine the on/off state of the keys, the LC75804E/W 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 DO) 615T(s) after starting a key scan. If the key data dose not agree and a key was pressed at that point, it
scans the keys again. Thus the LC75804E/W cannot detect a key press shorter than 615T(s).
KS1 *3 1
1
*3
KS2 *3
2
2
*3
KS3 *3
3
3
*3
KS4 *3
4
4
*3
KS5 *3
5
5
*3
KS6
6
6
T=
1
fosc
Key on
576T[s]
Note: *3. In sleep mode the high/low state of these pins is determined by the S0 and S1 bits in the control data. Key scan output signals are not output from
pins that are set low.
2. In normal mode
• The pins KS1 to KS6 are set high.
• 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 615T(s) (Where T= —fo1—sc ) the LC75804E/W outputs a key data read request (a
low level on DO) to the controller. The controller acknowledges this request and reads the key data. However, if
CE is high during a serial data transfer, DO will be set high.
• After the controller reads the key data, the key data read request is cleared (DO is set high) and the LC75804E/W
performs another key scan. Also note that DO, being an open-drain output, requires a pull-up resistor (between 1
and 10 kΩ).
Key input 1
Key input 2
Key scan
CE
615T[s]
615T[s]
Serial data transfer
DI
Serial data transfer Key address (43H) Serial data transfer
615T[s]
Key address
Key address
DO
Key data read request
Key data read
Key data read
Key data read
Key data read request
Key data read request
T=
1
fosc
No. 6266-17/37
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