PT6530 Datasheet, PDF (25/42 Pages) Princeton Technology Corp – LCD Driver IC

PT6530
6.7 KEY SCAN OPERATION FUNCTIONS
6.7.1 KEY SCAN TIMING
The key scan period is 288T(s). To reliably determine the on/off state of the keys, the PT6530 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 does not agree and a key was pressed at that point, it scans the keys
again. Thus the PT6530 cannot detect a key press shorter than 615T(s).
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.
6.7.2 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= ¹ ) the PT6530 outputs a key data read request (a low
fosc
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 PT6530 performs
another key scan. Also note that DO, being an open-drain output, requires a pull-up resistor (between 1 and 10KΩ).
V1.3
25
June 2010