Low power waveform, Operation in sleep mode, Display blanking – Rainbow Electronics Atmega169L User Manual
Page 214: Port mask, Atmega169v/l
214
ATmega169V/L
2514A–AVR–08/02
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 latch-
ing and Interrupt Flag is only set every second frame. Default and low power waveform
is shown in Figure 102 for 1/3 duty and 1/3 bias. For other selections of duty and bias,
the effect is similar.
Figure 102. Default and Low Power Waveform
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 external 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 137 for further details.
Before entering Power-down mode, Standby mode or ADC Noise Reduction mode with
synchronous LCD clock selected, the user have to disable the LCD. Refer to “Disabling
the LCD” on page 217.
Display Blanking
When LCDBL is written to one, the LCD is blanked after completing the current frame.
All segments 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.
Port Mask
For LCD with less than 25 segment terminals, it is possible to mask some of the unused
pins and use them as ordinary port pins instead. Refer to Table 95 for details. Unused
common pins are automatically configured as port pins.
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
COM0
SEG0 - COM0
Frame
Frame