Rainbow Electronics ATmega3290P_V - Manual (Page 223)

223
ATmega329/3290/649/6490
2552H–AVR–11/06
Mode of Operation
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 100. SEG0 - COM0 is
the voltage across a segment that is on, and SEG1 - COM0 is the voltage across a seg-
ment that is off.
Figure 100. Driving a LCD with One Common Terminal
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 segments. Although 1/3 bias can be selected 1/2 bias is most
common for these displays. Waveform is shown in Figure 101. SEG0 - COM0 is the volt-
age across a segment that is on, and SEG0 - COM1 is the voltage across a segment
that is off.
Figure 101. Driving a LCD with Two Common Terminals
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