PT6554_10 Datasheet, PDF (16/30 Pages) Princeton Technology Corp – LCD Driver IC

PT6554
KEY SCAN OPERATION UNDER THE SLEEP MODE
Under the Sleep Mode, the key scan output pins – KS1 to KS6 are set either to HIGH or LOW” State by the Sleep
Acknowledge Control Bits – S0 and S1. If a key that is located on one of the lines corresponding to a KS1 to KS6 pin that
has been set to “HIGH” is pressed, then the oscillation commences and the key scan operation is executed. 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 been 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. It must be noted that the Sleep Mode is not cleared. Please refer to the Sleep Mode Key Scan
example given below.
In the example below, Sleep Mode: S0=0, S1=1, KS6 Pin=”HIGH”.
Notes:
1. T=1/fosc, where fosc is the oscillation frequency.
2. In order to prevent erroneous operation due to sneak current in the KS6 scan output signal when keys on the KS1 to KS5 lines are pressed at the
same time, diodes must be connected as shown in the diagram above.
V1.4
16
June 2010