An LCD display is made of several segments such as pixels or complete symbols which can be made visible or invisible. A segment has two electrodes with a 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 SLCD controller is intended for monochrome passive liquid crystal display (LCD) with up to eight common terminals and up to 44 segment terminals.

Figure 1. LCD Panel - Segment/Common Terminals Connections

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.

The Segment LCD1 Xplained Pro has four common and 24 segment terminals.