Datasheet

226
ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET]
8284E–AVR–02/2013
24.3 Mode of operation
24.3.1 Static Duty and Bias
If all segments on a LCD have one electrode common, then each segment must have a unique terminal.
This kind of display is driven with the waveform shown in Figure 24-3. SEG0 - COM0 is the voltage across a seg-
ment that is on, and SEG1 - COM0 is the voltage across a segment that is off.
Figure 24-3. Driving a LCD with one common terminal.
24.3.2 1/2 Duty and 1/2 Bias
For LCD with two common terminals (1/2 duty) a more complex waveform must be used to individually control seg-
ments. Although 1/3 bias can be selected 1/2 bias is most common for these displays. Waveform is shown in
Figure 24-4 on page 226. SEG0 - COM0 is the voltage across a segment that is on, and SEG0 - COM1 is the volt-
age across a segment that is off.
Figure 24-4. Driving a LCD with two common terminals.
24.3.3 1/3 Duty and 1/3 Bias
1/3 bias is usually recommended for LCD with three common terminals (1/3 duty). Waveform is shown in Figure
24-5. SEG0 - COM0 is the voltage across a segment that is on and SEG0-COM1 is the voltage across a segment
that is off.
V
LCD
GND
V
LCD
GND
V
LCD
GND
-V
LCD
SEG0
COM0
SEG0 - COM0
Frame Frame
V
LCD
GND
V
LCD
GND
GND
SEG1
COM0
SEG1 - COM0
Frame Frame
V
LCD
GND
V
LCD
1
/
2
V
LCD
GND
V
LCD
1
/
2
V
LCD
GND
-1
/
2
V
LCD
-V
LCD
SEG0
COM0
SEG0 - COM0
Frame Frame
V
LCD
GND
V
LCD
1
/
2
V
LCD
GND
V
LCD
1
/
2
V
LCD
GND
-1
/
2
V
LCD
-V
LCD
SEG0
COM1
SEG0 - COM1
Frame Frame