ATMEGA169 ATMEL [ATMEL Corporation], ATMEGA169 Datasheet - Page 210

• Manufacturer Part Number: ATMEGA169
• Description: 8-bit Microcontroller with 16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

LCD Controller
Features
Overview
Definitions
210
ATmega169/V
The LCD Controller/driver is intended for monochrome passive liquid crystal display
(LCD) with up to four common terminals and up to 25 segment terminals.
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A simplified block diagram of the LCD Controller/Driver is shown in Figure 97. For the
actual placement of I/O pins, see “Pinout ATmega169” on page 2.
An LCD consists of several segments (pixels or complete symbols) which can be visible
or non visible. A segment has two electrodes with liquid crystal between them. When a
voltage above a threshold voltage is applied across the liquid crystal, the segment
becomes visible.
The voltage must alternate to avoid an electrophoresis effect in the liquid crystal, which
degrades the display. Hence the waveform across a segment must not have a DC-
component.
The PRLCD bit in “Power Reduction Register - PRR” on page 34 must be written to zero
to enable the LCD module.
Several terms are used when describing LCD. The definitions in Table 93 are used
throughout this document.
Table 93. Definitions
LCD
Segment
Common
Duty
Bias
Frame Rate
Display Capacity of 25 Segments and Four Common Terminals
Support Static, 1/2, 1/3 and 1/4 Duty
Support Static, 1/2, 1/3 Bias
On-chip LCD Power Supply, only One External Capacitor needed
Display Possible in Power-save Mode for Low Power Consumption
Software Selectable Low Power Waveform Capability
Flexible Selection of Frame Frequency
Software Selection between System Clock or an External Asynchronous Clock Source
Equal Source and Sink Capability to maximize LCD Life Time
LCD Interrupt Can be Used for Display Data Update or Wake-up from Sleep Mode
Segment and Common Pins not Needed for Driving the Display Can be Used as Ordinary
I/O Pins
Latching of Display Data gives Full Freedom in Register Update
A passive display panel with terminals leading directly to a segment
The least viewing element (pixel) which can be on or off
Denotes how many segments are connected to a segment terminal
1/(Number of common terminals on a actual LCD display)
1/(Number of voltage levels used driving a LCD display -1)
Number of times the LCD segments is energized per second.
2514P–AVR–07/06