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Mic1 Microprogramming Simulator

As explained in the documentation file, this software simulates the execution of microprograms based on the example machine given in Ch. 4 of Andrew S. Tanenbaum's Structured Computer Organization, 3rd ed. (Prentice-Hall, 1990). Note that his memory-mapped I/O is not supported by the simulator and that the range of memory addresses handled is much more limited that what is used in his text. The simulator gives a visual display of what happens in each subcycle (or cycle, etc.) of the microprogram. This can be useful in introducing students to microprogramming, since it is something that they cannot usually try in practice. With Mic1, students (or the instructor) can run small test microprograms, or even Tanenbaum's Mic-1 microprogram which interprets Mac-1 programs. (Mac-1 refers to his example conventional machine level. Note that Tanenbaum's microprogram interpreter has been modified to handle a Mac-1 HALT instruction.)

The simulator can be used in several ways with students in computer architecture & organization classes. First, students can run some of the example microprograms provided with the simulator. Then they can write and run their own microprograms. By using the microprogram interpreter that implements the Mac-1 machine language, students can run Mac-1 machine language programs, whether those supplied with the simulator (such as mic003.txt) or ones they write themselves. The most challenging type of project, however, is to have students invent a new Mac-1 machine language instruction and then to implement it by rewriting the microprogram interpreter. The author has used this as a contest in which part of the goal is to have students demonstrate their creativity in designing a useful Mac-1 instruction.

The Mic1 simulator and associated sample programs are made available as freeware. The latest version of the Mic1 microprogramming simulator runs under most versions of Windows. It was directly tested on Windows 95, 2000, and XP.

mic1.zip
A zip file containing the mic1.exe simulator, mic1doc.txt documentation, and sample microprograms.
mic1.exe
The simulator alone.
mic1doc.txt
The documentation file.
Drawing of the Mic1 Machine
Microinstruction Coding Sheet
Notes on simple microprogramming examples
More simple microprogramming examples
Used as a class exercise.
Microprogramming coding examples
Mac1 Notes
Notes on doing Mac1 machine language programming with this simulator.
Mac1 Instruction Set
Functions, Parameters, and Stack Frames in Mac-1 Machine Language
Notes on mic004.txt
Example of function call and return.
interprt.txt
Contains the microcode interpreter in microassembly language form. This is the interpreter which fetches, decodes, and executes Mac1 machine language instructions.
Microprogram interpreter notes
Traces how the interpreter fetches, decodes, and executes a few machine language instructions. Also dicusses how to add your own machine language instruction to the instruction set.
The following individual sample Mic1 and Mac1 programs are available:
- mic001.txt
  Simple microprogram to read and push one item.
- mic002.txt
  Microprogram that does a read, boolean not, and right shift.
- mic003.txt
  Shows a loop in machine language.
- mic004.txt
  Shows function call and return in machine language.
- mic005.txt
  Shows an error due to an illegal field value.
- mic006.txt
  Shows the error given if a register number is missing.
- mic007.txt
  Microprogram that illustrates overflow upon addition.
- mic008.txt
  Illustrates subtraction in microcode.
- mic009.txt
  Illustrates subtraction in microcode.
- mic013.txt
  Shows an error due to incorrect attempt to read.
- mic014.txt
  Shows an error due to incorrect attempt at a write.
- mic015.txt
  Machine language program to push the sum of 2 constants.
- mic022.txt
  Adds and tests a new machine language instruction named NEGA.
- mic024.txt
  Shows an error due to trying to write to code area.
- mic025.txt
  Shows how to do a FOR loop in microcode.

Instructor: Br. David Carlson

Maintained by: Br. David Carlson
Last updated: April 03, 2014
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