CP316: Microprocessor Systems and Interfacing

Liquid Crystal Display (LCD) Prelab or Postlab

To be done in your lab notebook.

1. Pin 3 on the LCD is the contrast voltage for the display. The typical circuit uses a potentiometer wired as a voltage divider to allow the contrast voltage to be adjusted. Normally, the circuit does not show a capacitor. The QwikFlash board uses a fixed voltage circuit.
   1. Sketch the contrast voltage circuit for the QwikFlash board.
   2. At what voltage does the QwikFlash board have the contrast voltage set?
   3. Why is the capacitor there?
   4. Redraw the contrast voltage circuit to allow adjustment, i.e. using a potentiometer.
      
      
2. The Hitachi controller has a lot of different commands. How does it figure out which command is being sent?
   
   
3. The QwikFlash board ties the R/W line permanently low. With the R/W line permanently at write, the read commands for the controller cannot be used and all timing must be delay based. Using the timing diagram for the write operation from either LCD manual or the text as a starting point, redraw the timing diagram without the R/W line and remove all R/W associated timings. For all remaining time intervals, write the actual minimum time (in ns) instead of the symbol.
   
   
   Demonstration - Explain your results for the above questions.