PT6554_10 Datasheet, PDF (15/30 Pages) Princeton Technology Corp – LCD Driver IC

PT6554
KEY SCAN OPERATING UNDER THE NORMAL MODE
Under the Normal Mode, the Key Scan Output Pins – KS1 to KS6 are set to HIGH. When a key is pressed, a key scan
operation commences. The keys are scanned until all keys are released. For multiple key press operation, a multiple key
press is valid only if multiple key data bits have set and verified by the key scan.
If a key is pressed longer than 800T(s), PT6554 outputs a key read data request (DO is set to “LOW” level) to the
controller. The controller acknowledges the request and reads the key data. It must be noted that if CE is HIGH during a
serial data transfer, then DO is set to “HIGH”.
After the controller reads the key data, the key data request is cleared (DO is set to HIGH) and another key scan
operation is performed.
Notes:
1. T=1/fosc, where fosc is the oscillation frequency.
2. DO is an open – drain output and requires a pull-high resistor between 1KΩ to 10KΩ.
V1.4
15
June 2010