CPE 315
Professor Stearns
Winter 2008
Laboratory Exercise #5 - Control Unit
Due at the end of lab Feb. 19
You may do this exercise with a partner if you wish.

• Get your Control Unit design started.
  
• Design the complete SLT circuit for your alu.
  

1. ROM Examples
   Build the sim ROM Examples Unless you have a really good reason, you should use a ROM for both ALU Control and Control.
   

2. Control Unit Design
   Design a small part of your control unit (e.g. R-type instructions)
   

3. Control Unit Implementation
   Implement the small part of your control unit in a ROM.
   Show your working control unit to Prof. Stearns
   

4. Complete the SLT design
   The SLT circuit in the textbook only works for 2's complement SLT instructions and only if there is no subtract overflow.
   Do some manual calculations to verify this yourself; show those calculations to Prof. Stearns
   

   Design a complete SLT circuit that handles:
   

   1. 2's complement overflow
      
   2. Unsigned SLT instructions
      
   Represent your design in equations:

   Set = unsigned' ^ V' ^ Result[31]    // Your Lab #3 circuit
         + unsigned' ^ V ^ ????         // Finish for this exercise
         + unsigned ^ ?????             // Finish for this exercise 
   

   Note: you need to add a new control signal that tells the ALU it is doing an unsigned SLT.
   Recall the ALU doesn't know the difference between 2's complement and unsigned math. That principle now changes for SLT instructions.
   

   Show your design to Prof. Stearns