Description
In this homework, you will run processes on a simulated Intel8080 CPU emulator. The emulator is
provided as a C++ class. Your job in this homework will be to write a few assembly programs to run
on this emulator. However since you will need some OS systems calls and we do not have any OS
available, you will also have to write some simple OS system calls mainly for screen input and
output. Here are the files that we provide with this homework:
8080Book.pdf : Good book on 8080 Assembly programming
8080_Z80 Instruction Set.pdf : reference for 8080 assembly programming
8080emu.cpp : Emulator implementation for 8080. You will not change this file
8080emuCPP.h: Emulator interface for 8080. You will not change this file
gtuos.h : sample header for GTUOS. You will rewrite this file
gtuos.cpp : sample implementation for GTUOS. You will rewrite this file
main.cpp : sample main function for this HW. You will rewrite this file
sum.asm: Adds numbers from 0 to 10 and prints the results on screeen.
sum2.asm : Adds numbers from 0 to 10 and prints the results on screeen using a different system
call.
printstr.asm : 8080 Assembly file that prints “Hello world” on screen.
You need to use an assembler to produce the executable machine code for your emulator. Use the
simple assembler at , http://asdasd.rpg.fi/~svo/i8080/ which helps a lot in writing the assembly
code. You can directly download the executable .com file from this site.
There are two main tasks for you to do in this homework.
First, you need to implement a number of GTUOS systems calls as descibed below
Call Params to pass Function How many
cycles
PRINT_B Register A = 1,
Register B holds the
value to be printed
Prints the contents of register B on
the screen as a decimal number.
10
PRINT_MEM Register A = 2,
Register BC = adress
Prints the contents of the memory
pointed by registers B and C as a
decimal number.
10
READ_B Register A = 3,
Register B will hold the
value
Reads an integer from the keyboard
and puts it in register B.
10
READ_MEM Register A = 4,
Register BC = adress
Reads an integer from the keyboard
and puts it in the memory location
pointed by registers B and C
10
PRINT_STR Register A = 5,
Register BC = adress
Prints the null terminated string at
the memory location pointed by B
and C
100
READ_STR Register A = 6,
Register BC = adress
Reads the null terminated string
from the keyboard and puts the
result at the memory location
pointed by B and C
100
You will rewrite the two files (gtuos.h, gtuos.cpp) to implement the above system calls and you will
write another file (main.cpp) to use your OS with the 8080 CPU. Use the sample main file as a
guide.
You will also write and test the following assembly files. Use the provided sample assebly files to
learn about how to use the assembler and how we call the OS.
1. PrintNumbers.asm: file that prints integers from 0 to 50 on the screen. Each number will be
printed on a new line.
2. PrintNumbersRev.asm: file that prints integers from 100 down to 50 on the screen. Each
number will be printed on a new line.
3. Sort.asm: file that sorts the numbers 12, 34, 53, 2A, 5B, 6F, 33, 21, 7C, FF, BA, CB, A1,
1A, 3B, C3, 4A, 5D, 62, A3, B1, 5C, 7F, CC, AA, 34 in increasing order and prints the
results on the screen. Use DW assembler directive to give the initial numbers.
4. Search.asm: reads an integer from the keyboard and makes a linear search on the integer list
above. If found prints the memory address else prints “error”
5. test.asm: a file that tests each of the system calls one by one.
Your program should work
sim8080 exe.com debugFlag
There should be parameters for the program name and debug flag. Sim8080 is your program,
exe.com will be produced by the assembler, and the debug will work as follows
◦ sim8080 exe.com 1 : will read the program from exe.com. In debug mode 1, the
status of the CPU will be printed to the screen after each instruction execution. At the
end of the simulation, the whole memory will be saved to exe.mem as a text file of
hexedecimal numbers. Each line of the file will start with the memory addres, then it
will show 16 bytes of hexadecimal numbers separated with spaces.
◦ In Debug mode 0, the program will be run and the contents of the memory will be saved
as in Debug mode 1.
◦ In Debug mode 2, after each instruction execution, the CPU state will be displayed. Your
simulation will wait for an from the keyboard and it will continue for the next tick. The
contents of the memory will be saved as in Debug mode 1.
All three modes will display the total number of cycles used by the program at the end of the
executions.
We will provide the submissin instructions in a separate document. You should strictly follow these
instructions otherwise your submission may not get graded.
