dobby

University of Southampton second year ELEC2204 Computer Engineering coursework.

Directory structure

.
├── Doxyfile
├── Makefile
├── README.md
├── inc
│   ├── alu.h
│   ├── decoder.h
│   ├── dobby.h
│   ├── examples.h
│   ├── global.h
│   ├── memory.h
│   ├── opcodes.h
│   ├── print.h
│   └── registers.h
└── src
    ├── alu.c
    ├── decoder.c
    ├── dobby.c
    ├── examples.c
    ├── memory.c
    ├── print.c
    └── registers.c

Build instructions

For this project I have made a Makefile to simplify compilation of the files and their dependencies. This means that if one or two files are changed the compiler only rebuilds the changed files, thus reducing compile time. To run the Makefile there are a number of options,

make, builds code to dobby executable.
make debug, builds the same as make but invokes the DEBUG flag which writes internal signal values to dobby.log on each processor tick.
make clean, cleans directory of build files (build/, dobby and doxygen/).
make docs, calls Doxygen to generate code documentation.
make open, opens generated Doxygen in web browser.

 CC     src/alu.c
 CC     src/decoder.c
 CC     src/dobby.c
 CC     src/examples.c
 CC     src/memory.c
 CC     src/print.c
 CC     src/registers.c

Example assembly

In examples.c there are a number of example assembly programs. These programs are then stored in an array called *examples. The examples are then copied into memory when the user presses certain number keys.

Output

dobby.c uses and ncurses interface to display the current state of the cpu, values on the data/address bus, inputs and operations passed to the ALU, data in particular addresses in memory as well as the data stored in the program counter, instruction register and accumulator.

By pressing <enter> (actually, any key besides <q>) the system will step through to the next state of operation. This is to help debug the operation of the CPU.

The <u> and <d> keys move the memory table up/down. It is unrealistic to print all 256 addresses to the screen at the same time.

Start up instructions

Dobby debugging suite.
Other keys increment program counter.
u: Move address list up.
d: Move address list down.
q: Quit program.
1: Program #1
2: Program #2

Documention

Futher documentation in the form of a compiled doxygen website can be found here.