PT6552 Datasheet, PDF (15/22 Pages) Princeton Technology Corp – ½ Duty LCD Driver with On-Chip Key Input Function

PT6552
2. CONTROLLER KEY DATA READING UNDER INTERRUPT CONTROL
When determining key on/of and reading key data, the controller must confirm the state of DO output when CE is low.
When DO is low, the controller recognizes that a key has been pressed and reads the key data. After the time t8, the next
key on/off determination and reading key data must be confirmed by the state of DO output when CE is low. During this
operation t8 must obey the following condition:
t8 > t4.
If key data is read when DO is high, the key data (KD1 to KD30) and the sleep acknowledge data (SA) be invalid.
FLOWCHART
TIMING CHART
T=1/fosc
t3: Key scan execution time (800T [s]) when the key scan data for two key scans agrees.
t4: Key scan execution time (1600T [s]) when the key scan data for two key scans does not agree and a key scan is
executed again.
t5: Key address (43H) transfer time.
t6: Key data read time.
V1.3
15
July 2010