Lecture 17 Objectives
At the end of today's class you should
KNOW:
- the difference between memory-mapped I/O and the use of specialized I/O
instructions
- how the technique of polling is employed to effect an asynchronous
data transfer
- how the LC-3 uses polling to do input from the keyboard and output to
the display
BE ABLE TO:
- write a simple LC-3 assembly language routine that uses polling
to input or output a character
Sample Exam Question:
Write the LC-3 assembly language instructions that will input 5 characters
from the keyboard and echo each character as an 'X'. You should access the
keyboard and display devices directly (do not use TRAP to solve this problem).