ECE 4510/5530 Microcontroller Applications
Fall 2008
Homework Assignment #2
Total: 60pts.
Due 3:30pm, Monday, September 22, 2008
Write a syntactically correct 9S12 assembly program that will toggle Bits 2and 5of
Port T (PT2 and PT5)at approx. 200ms intervals such that PT2 and PT5 will be each
other’s complement. The program should run in an infinite cycle. The addresses to
access to PORTT and DDRT, respectively, are posted in the Labs Section of the Class
Web Page. The 200ms timing should be implemented as a "software delay", i.e., the
time needed for the program to leave a loop after its entry on top should be
approximately 200ms. The number of clock cycles for fetching and executing
instructions are published in the CPU12 Reference Manual (Tables A-1,andA-2), and
one clock cycle takes 125ns. The core of the delay loop should take approx. 50
microseconds. In order to prove that your program would do the job, you should show
your calculations (i.e., develop a formula for your approach) to achieve the inner delay
of 50 microseconds, and the total delay of 200ms. Choose the code, data, and variable
locations for your program such that it could run on the system in the Lab but you are not
required to prove that it has actually run. Turn in your assembled .lst file and comment
on your code for full credit. (60 pts)