42.1 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 LCD controller is intended for monochrome passive liquid crystal display (LCD) with up to 8 common terminals and up to 44 segment terminals. A charge pump provides LCD display supply which can be higher than supply voltage of the device. Each LCD pin, segment or common terminals, can be configured as general purpose I/O pins if not driven by LCD controller.

Several features such as character mapping, automated characters string display, autonomous animation are implemented to reduce CPU load and power consumption.

Figure 42-1. LCD Panel - Segment/Common Terminals Connections

Note: In order to avoid degradation due to electrophoresis in the liquid crystal, the waveform of the voltage across a segment must not have a DC component.