HL15604
8. Key Scan Function
1) Key Scan Timing
The key scan period is 384T. The HL14104 scans the key twice and determines
that a key has been pressed when the key data agrees. It outputs a key data read
request 800T after starting a key scan. If the key data does not agree and a key
was pressed at that point, it scans the key again.Thus the HL14104 cannot detect
a key press shorter than 800T.
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KS1
KS2
KS3
KS4
KS5
KS6
1
1
2
2
3
3
4
4
5
5
6
6
768T
Key on
*) In sleep mode the high / low state of these pins is determined by the S0,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 800T ( where T=1/fosc ) the HL14104
outputs a key data read request (a low level on SO pin) to the controller. The
controller acknowledges this request and reads the key data. However, if CE
is high during a serial data transfer, SO will be set high.
• After the controller reads the key data, the key data read requests is cleared (
SO pin is set high ) and the HL14104 performs another key scan. Also note
that SO pin, being an open-drain output, requires a pull-up resistor.
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HYNIX [ HYNIX SEMICONDUCTOR ]
