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ManualsBrandsMICROCHIP TECHNOLOGY ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller TQFP 64 (14x14) 8-Bit 20 MHz I/O number 54
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ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET]
8284E–AVR–02/2013
Figure 24-7. Default and low power waveform.
24.3.6 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 Cali-
brated 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 buf-
fer is enabled and an external clock can be input on Timer Oscillator 1 (TOSC1) pin instead of a 32kHz XTAL. See
”Asynchronous operation of Timer/Counter2” on page 151 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 231.
24.3.7 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.
24.3.8 Port Mask
For LCD with less than 25/40 segment terminals, it is possible to mask some of the unused pins and use them as
ordinary port pins instead. Refer to Table 24-3 on page 234 for details. Unused common pins are automatically
configured as port pins.
24.4 LCD Usage
The following section describes how to use the LCD.
24.4.1 LCD Initialization
Prior to enabling the LCD some initialization must be preformed. The initialization process normally consists of set-
ting the frame rate, duty, bias and port mask. LCD contrast is set initially, but can also be adjusted during
operation.
Consider the following LCD as an example:
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