PT6555 Datasheet, PDF (20/28 Pages) Princeton Technology Corp – LCD Driver IC

PT6555
CONTROLLER KEY DATA READ TECHNIQUES
When the controller receives a key data read request from PT6555, it performs a key data read acquisition operation
using either the Timer Based Key Data Acquisition or the Interrupt Based Key Data Acquisition.
TIMER BASED KEY DATA ACQUISITION TECHNIQUE
Under the Timer Based Key Data Acquisition Technique, the controller uses a timer to determine the states of the keys
(ON or OFF) and read the key data. Please refer to the flowchart below.
Every t7 period, the controller checks the state of DO when the CE is at “LOW” level. If DO is “LOW”, then the controller
validates that a key has been pressed and performs a key data read operation. Please refer to the timing diagram below.
It must be noted that if the key data read operation is performed when the DO is “HIGH”, the read key data (KD1 to KD30)
and the sleep acknowledge bit will not be valid.
V1.1
20
August, 2009