EE 476: Homework 3
- 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?
- Discuss how you will implement the required
The scheme must be as accurate as the crystal.
- How accurate is the crystal? Find a data sheet.
Copyright Cornell University Dec 2006