EE 476: Homework 3

  1. The keypad scanning routine given in Lab 3 uses a scheme where the upper and lower nibbles of an i/o register are alternately used for input and output. Figure out a way to scan a 4x4 keypad which drives the vertical wires as 4 output bits and reads the horizontal wires as inputs, with no i/o swapping. Does either scheme have an advantage?
  2. Discuss how you will implement the required day:hrs:min clock. Note that any scheme which involves reloading timer0 will not be accurate enough. You must use timer1

Copyright Cornell University Jan 2004