4.2. PICDEM Liquid Crystal Display

• LCD layout and connections

• LCD test program

• BCD count program

The plain 3.5-digit parallel liquid crystal display (LCD) is driven directly from the MCU, occupying 15 of the I/O pins. The usual alternative to this arrangement is to use a serial LCD, which can be driven via the RS232 port. This occupies only one or two pins, but it is more expensive, as it contains its own microcontroller.

LCD Connections

The parallel LCD is operated by specific combinations of inputs that enable the segments as required (Figure 4.7). The segments are designated A to G for each seven-segment digit, with digits numbered 1 to 4 from the right. The most significant half digit (4) has only segments B and C, displaying only ‘1’. ...

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