PT6554_10 Datasheet, PDF (14/30 Pages) Princeton Technology Corp – LCD Driver IC

PT6554
SLEEP MODE
The Sleep Mode is enabled when any one of the Sleep Acknowledge Control Bits – S0 or S1 is set to “1”. Under the
Sleep Mode, the all the segment and common driver outputs are set to “LOW” level and the oscillation operation is
terminated. Oscillation operation will only commence again if a key is pressed. Please note that this reduces power
dissipation. The Sleep Mode is cleared when both control bits – S0 and S1 are set to “0”.
It should be noted, however, that the output pins – SG1/P1 and SG2/P2 might still be used as General Purpose Output
Ports by setting the control bits – P0 and P1 even under the Sleep Mode. In other words, the Sleep Mode does not in
anyway affect the SG1/P1 and SG2/P2 pins from being used as General Purpose Output Ports.
KEY SCAN OPERATION
KEY SCAN TIMING
PT6554 scans the keys twice (reads the key data twice) and if the key data matches, this key is defined as PRESSED (or
ON ). A key scan period is equivalent to 384T (s). 800T (s) after the key scan commences, PT6554 outputs a key data
read request. If the key data from the does not match and a key was pressed at that point, the keys are scanned again.
It must be noted that PT6554 cannot detect a key which is pressed shorter than 800T (s).
Notes:
1. T=1/fosc where fosc=oscillation frequency
2. The Sleep Mode, the state of these pins is determined by the control bits – S0 and S1. Key Scan signals are not outputted from pins that are set to
“LOW” Level.
V1.4
14
June 2010