PT6554_10 Datasheet, PDF (23/30 Pages) Princeton Technology Corp – LCD Driver IC

PT6554
INTERRUPT BASED KEY DATA ACQUISITION TECHNIQUE
Under the Interrupt Based Key Data Acquisition Technique, the controller uses interrupts to determine the state of the
keys (ON or OFF) and read the key data. Please refer to the flow chart diagram below.
Every t8 period, the controller checks the state of the DO Pin when CE is at “LOW” state. If the DO is at “LOW” level, then
the controller validates that a key has been pressed and a key data read operation is performed. Please refer to the
timing diagram below. It must be noted however, that if a key data read operation is performed when DO is held “HIGH”,
the read key data – KD1 to KD30 and the sleep acknowledge bit SA will not be valid.
Notes:
1. t8 > t4
2. t3 is the Key Scan Execution Time when the key data matches (2 key scan operations): 800T (s)
3. t4 is the Key Scan Execution Time when the key data do not match (2 key scan operations) and the key scan operation is once again performed:
1600T (s).
4. T=1/fosc where fosc is the oscillation frequency.
5. t5 is the Key Address Transfer Time (43H)
6. t6 is the Key Data Read Time
7. T7 > (t5 + t6 + t4)
V1.4
23
June 2010