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LCD Driver IC
PT6584
KEY SCAN OPERATION FUNCTIONS
KEY SCAN TIMING
The key scan period is 384T(s). To reliably determine the on/off state of the keys, the PT6584 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) 800T(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 PT6584 cannot detect a key
press shorter than 800T(s).
KS1
KS2
KS3
KS4
∗
∗
∗
∗
1
1
2
2
∗
∗
∗
∗
3
3
∗
∗
4
4
KS5
KS5
5
5
6
6
768T [s]
Key on
1
fosc
T=
Note:
*: 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.
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.
1
• If a key is pressed for longer than 800T(s) (Where T=
) the PT6584 outputs a key data read
fosc
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
PT6584 performs another key scan. Also note that DO, being an open-drain output, requires a
pull-up resistor (between 1 and 10KΩ).
PT6584 V1.1
- 17 -
August, 2006
PTC [ PRINCETON TECHNOLOGY CORP ]
