Interface LCD with ease

Posted on Nov 3, 2012

The circuit in Figure 1 saves I/O pins. It uses an 8051 µC, and only four I/O pins (P1.0 to P1.3) drive the LCD, instead of the 11 pins other displays require. Data transfers in a serial mode through the P1.0 port of the µC. The µC interfaces to Pin 2 of IC1, a 74HCT4094 8-bit shift register. Serial data advances on every clock pulse and transfers to the shift register. The register converts the serial data to parallel data, available on the output pins Q0 to Q7. The P1.1 port of the µC provides the clock.

The data bus, D0 to D7, of the LCD module connects to the shift register`s outputs. Software carries out the data transformation and displays the result on the LCD (Listing 1). The same design can drive various types of alphanumeric LCDs-for example,

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