Microprogramming

The lab asks you to interpret some microprograms and then write write your own simple microprograms.

Resources: Throughout this lab, you will need to consult Figures 4-8, 4-9, and 4-10 (section 4.2) in Tanenbaum's text.

Collaboration: As with the work for the previous labs, the following steps are to be done on paper collaboratively. Everyone should work in a group of two (preferred) or three students; within a group, each person should take responsibility for leading discussion for some of the problems.

Steps for this Lab: In the following, assume register A contains the address of the variable X, register B contains the address of variable Y, and register C contains the address of variable Z.

1. Consider Microprogram 1 which implements the Pascal statement Z := X - Y .
   This code may be printed with the command:

   dvips ~walker/public_html/courses/211/labs/micro-code-1.dvi
   

   1. Write a sentence or two to explain why each statement does what is claimed by the comment field.

   2. Explain why the values in the the fields containing dashes (-) do not matter.

   3. Why do you think the value of X is stored in a register (Register D), but the value of Y is never transferred to one of the sixteen internal register?

   4. Why do you think the code uses Register D for X rather than Register A, B, or C?

2. Consider Microprogram 2 This code may be printed with the command:

   dvips ~walker/public_html/courses/211/labs/micro-code-2.dvi
   

   Annotate each line of the code, following the approach used for the comments from step 1.

   Make a summary statement indicating the overall effect of this code (e.g., the code in step 1 computed Z := X - Y ).

3. Consider Microprogram 3 This code may be printed with the command:

   dvips ~walker/public_html/courses/211/labs/micro-code-3.dvi
   

   Annotate each line of the code, following the approach used for the comments from step 1.

   Make a summary statement indicating the overall effect of this code.

4. Write microcode for the Pascal statement

   Z := 8*X - 17;
   

Work to be turned in:

• Write out your comments for step 1.

• Print out the microcode for steps 2 and 3, and write your annotations and summary statement on the printout.

• Write out the microcode for step 4 using microcode form for each.
  This form may be printed with the command:

  dvips ~walker/public_html/courses/211/labs/micro-code-form.dvi
  

  For each instruction, indicate a 0 or 1 only in those fields where the value matters. Place a dash (-) in fields where the values are ignored. Also, be sure to annotate your code appropriately.

This document is available on the World Wide Web as

     http://www.math.grin.edu/~walker/courses/211/labs/lab.microprogramming.html