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XMEGA B [DATASHEET]
8291B–AVR–01/2013
25.
LCD – Liquid Crystal Display
25.1
Features
Display Capacity up to 40 Segment and up to 4 Common Terminals
Supports up to 16 GPIO's
Shadow Display Memory Gives Full Freedom in Segment Update
ASCII Character Mapping
Swap Capability Option on Common and/or Segment Terminal Buses
Supports from Static up to 1/4 Duty
Supports Static and 1/3 Bias
LCD Driver Active in Power Save Mode for Low Power Operation
Software Selectable Low Power Waveform
Flexible Selection of Frame Frequency
Programmable Blink Mode and Frequency
Blink on two Segment Terminals
Uses Only 32kHz RTC Clock Source
On-chip LCD Power Supply
Software Contrast Adjustment Control
Equal Source and Sink Capability to Increase LCD Life Time
Extended Interrupt Mode for Display Update or Wake-up from Sleep Mode
25.2
Overview
An LCD display is made of several segments (pixels or complete symbols) which can be visible or invisible. A segment
has two electrodes with liquid crystal between them. These electrodes are the common terminal (COM pin) and the
segment terminal (SEG pin). 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, this effect degrades
the display. Hence the voltage waveform across a segment must not have a DC-component.
The LCD controller is intended for monochrome passive liquid crystal display (LCD) with up to 4 Common terminals and
up to 40 Segments terminals. If the application does not need all the LCD segments available on the XMEGA, up to 16 of
the unused LCD pins can be used as general purpose I/O pins.
The LCD controller can be clocked by an internal or an external asynchronous 32kHz clock source. This 32kHz oscillator
source selection is the same as for the Real Time Counter (RTC).
Dedicated Low Power Waveform, Contrast Control, Extended Interrupt Mode, Selectable Frame Frequency and Blink
functionality are supported to offload the CPU, reduce interrupts and reduce power consumption.
To reduce hardware design complexity, the LCD includes integrated LCD buffers, an integrated power supply voltage
and an innovative SWAP mode. Using SWAP mode, the hardware designers have more flexibility during board layout as
they can rearrange the pin sequence on Segment and/or Common Terminal Buses.
Содержание XMEGA B
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