ATmega169P datasheet(239/393 Pages) ATMEL

239 / 393 page

239

8018N–AVR–08/09

ATmega169P

23.3.5

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 voltage. Consequently data latching and Interrupt Flag is only set

every second frame. Default and low power waveform is shown in Figure 23-7 for 1/3 duty and

1/3 bias. For other selections of duty and bias, the effect is similar.

Figure 23-7. Default and Low Power Waveform

23.3.6

Operation in Sleep Mode

When synchronous LCD clock is selected (LCDCS = 0) the LCD display will operate in Idle

mode and Power-save mode with any clock source.

An asynchronous clock from TOSC1 can be selected as LCD clock by writing the LCDCS bit to

one when Calibrated Internal RC Oscillator is selected as system clock source. The LCD will

then operate in Idle mode, ADC Noise Reduction mode and Power-save mode.

When EXCLK in ASSR Register is written to one, and asynchronous clock is selected, the exter-

nal clock input buffer is enabled and an external clock can be input on Timer Oscillator 1

(TOSC1) pin instead of a 32 kHz crystal. See ”Asynchronous operation of the Timer/Counter” on

page 150 for further details.

Before entering Power-down mode, Standby mode or ADC Noise Reduction mode with synchro-

nous LCD clock selected, the user have to disable the LCD. Refer to ”Disabling the LCD” on

page 243.

23.3.7

Display Blanking

When LCDBL is written to one, the LCD is blanked after completing the current frame. All seg-

ments and common pins are connected to GND, discharging the LCD. Display memory is

preserved. Display blanking should be used before disabling the LCD to avoid DC voltage

across segments, and a slowly fading image.

VLCD

3VLCD

GND

VLCD

3VLCD

GND

VLCD

3VLCD

GND

-1/3VLCD

-2/3VLCD

-VLCD

SEG0

COM0

SEG0 - COM0

Frame

VLCD

3VLCD

GND

VLCD

3VLCD

GND

VLCD

3VLCD

GND

-1/3VLCD

-2/3VLCD

-VLCD

SEG0

COM0

SEG0 - COM0

Frame

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