UCR CS122A, Fall 2005
Prof. Frank Vahid
Homework 2

Working in groups is encouraged. 10% extra credit for groups of 3 or
more working together for an hour or more. Write down each others'
names, and when/where you met. Every student should still solve
every problem and submit his/her own solutions; working together is 
useful to understand the problems, discuss solution ideas,
and compare answers.

This homework should be submitted ELECTRONICALLY using the CS&E
department's turnin server. Expected time is 2-3 hours -- please record
and report your actual time per problem. Start early!

All VHDL code should be generally suitable for synthesis using modern 
commercial FPGA synthesis tools. All code, VHDL or C, should be
reasonably concise. 


1. Create a system that simply pulses an output P high very briefly 
   (e.g., 1 clock cycle) every 1 second.  Create this system:
   (a) Using an FSMD captured in a single VHDL process. Assume an input 
       to your system is a 1 MHz clock named clk. You need only show
       the process, not the complete VHDL code. 
   (b) Using a microcontroller coded in C, assuming the microcontroller
       described at the bottom of this homework. Show the main and the
       ISR contents. 

2. Repeat the above problem, but create a pulse Q that is high 0.5 seconds
   seconds and low 0.5 seconds. 

3. Create a system that waits for an input B to become 1, and then
   lights three lights L, M, N in sequence: L for 1 second, then
   M for 1 second, then N for 1 second. 
   (a) Using one or more VHDL processes. 
   (b) Using a microcontroller coded in C, assuming the microcontroller
       described at the bottom of this homework. Show the main and the
       ISR contents. 

4. (a) Combine the systems in 1(a) and 3(a) into a single system
       that generates the pulse on P, and meanwhile also waits for the
       button B and then lights three lights. Use as many processes as
       you see fit. 
   (b) Combine the systems in 1(b) and 3(b) into a single system,
       using a microcontroller coded in C, assuming the microcontroller
       described at the bottom of this homework. Show the main and the
       ISR contents. 
          

MICROCONROLLER: For the above problems that refer to a microcontroller
described here, assume you are using a microcontroller with the following:
   * an external interrupt input Int1 that causes a call to an interrupt
     service routine names ISR_Int1(). 
   * an internal 16-bit timer that can be set by writing to the following
     registers, accessed as global variables in C:
       - short int timer1init: starting count value, counts down to 0
       - int timer1enable: set to 1 to enable counting, 0 to disable
       - int timer1wrap: set to 1 to wrap around to starting count value
                         each time the counter hits 0
       - int timerdir: counts down if 0, up if 1.
   * an internal interrupt generated by timer1 hitting 0, causing a
     call to ISR_Timer1().
   * 8-bit ports P0, P1, P2 and P3 accessible as global variables, each 
     also accessible as individual bits (e.g., P0.0-P0.7).
   * A clock with a period of 100 nanoseconds.