CSE466 Assignment 1: Due Monday 10/2

This assignment is a little longer than a typical 3-pointer, so it will be worth 5-points and it is due on Monday 10/2

A. Describe a strategy, using the hardware resources of the 8051, to measure the fan speed and detect errors as in the introductory example. Hint: consider the use of timers and interrupts, see the AT89 Series Hardware Description for ideas. 

Answer. I forgot to list it here, but the example presented in class had a clock speed of 4Mhz. At that oscillator speed the maximum count on timer zero at a 30Hz fan speed is (4M/12)/30 = ~11K. Setup timer-2 in capture mode and enable T2EX interrupts so that the timer will stop on the falling edge of T2EX. After we read the timer value in the external interrupt routine, we clear and restart the timer. 

B. What factors might affect with the accuracy of your measurement?

As long as no interrupts are missed due to processor occupation with other tasks, the solution is accurate to a single machine cycle. 

C. Write the 8051 assembly program including reset code, interrupt routine(s), hardware initialization and main execution loop to implement to perform fan speed measurement and verification. I don't mean for you to worry too much about syntax for 8051 assembly programs.

In my version, I went ahead and added the code to check for the case that the fan is moving too slow. There are at least three ways that this code can fail in real operation. Identify at least two of these failure modes and make any changes or additions necessary to catch them. Note: I am not looking for bugs in my code, If I made an obvious programming error, please fix it, but it won't count against the two items!