Datasheet

227
ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET]
8284E–AVR–02/2013
Figure 24-5. Driving a LCD with three common terminals.
24.3.4 1/4 Duty and 1/3 Bias
1/3 bias is optimal for LCD displays with four common terminals (1/4 duty). Waveform is shown in Figure 24-6 on
page 227. SEG0 - COM0 is the voltage across a segment that is on and SEG0 - COM1 is the voltage across a seg-
ment that is off.
Figure 24-6. Driving a LCD with four common terminals.
24.3.5 Low Power Waveform
To reduce toggle activity and hence power consumption a low power waveform can be selected by writing LCDAB
to one. Low power waveform requires two subsequent frames with the same display data to obtain zero DC volt-
age. Consequently data latching and Interrupt Flag is only set every second frame. Default and low power
waveform is shown in Figure 24-7 for 1/3 duty and 1/3 bias. For other selections of duty and bias, the effect is
similar.
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
-
1
/
3
V
LCD
-
2
/
3
V
LCD
-V
LCD
SEG0
COM0
SEG0 - COM0
Frame Frame
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
-
1
/
3
V
LCD
-
2
/
3
V
LCD
-V
LCD
SEG0
COM1
SEG0 - COM1
Frame Frame
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
-
1
/
3
V
LCD
-
2
/
3
V
LCD
-V
LCD
SEG0
COM0
SEG0 - COM0
Frame Frame
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
V
LCD
2
/
3
V
LCD
1
/
3
V
LCD
GND
-
1
/
3
V
LCD
-
2
/
3
V
LCD
-V
LCD
SEG0
COM1
SEG0 - COM1
Frame Frame