ECE2030 SPIM HOMEWORK Getting Familiar with SPIM DUE Nov 15 2002 Type in the following program using a text editor not a word processing package and execute it using PCSpim PAY ATTENTION TO THE SPACES IN THE ASCII DIRECTIVES There is a bug in PCSpim you have to leave a blank line at the end of the program To become familiar with the simulator it is useful to go through the following sequence of steps FIRST download simulator and run through the on line tutorials in the NEXT Section of the notes labeled PCSpim Tutorial Load the program into SPIM If you typed it in correctly it should load with no errors If there are typographical errors then a dialog window will pop up with the line number Other wise open the Console window and you can check the error message Continue to edit load until all errors are taken care of Run the program Answer the questions in Problem 1 and see the results The program should run with no problem Look in the data segment It will be filled with values starting at address 0x10010000 These values are product of the data directives in the program Check the text segment You will see instructions at each successive address in the text segment Learn to associate addresses with instructions Open the registers window and you will see the contents of all 32 registers Check the register s contents before and after running the program 1 2 3 4 Answer the following questions After loading the sample program on following page into the SPIM simulator what are the contents of the second third and fourth word in memory Indicate the type of computer you are using to run the SPIM simulator and after looking at the contents of the data segment indicate if the machine uses big endian or little endian convention to store words How many bytes of data are being used in the data segment At what address does the data segment begin SPIM Sample Program INSERT YOUR NAME ECE 2030 E or F SPIM Homework 1 Comments begin with the character Begin the data segment declare variables data asciiz SPIM is COOOOL byte 0xF2 align 2 enforce word alignment word 0xF28343AA num1 word 89 num2 word 7 result word 0 result word 0 text lw t0 num1 lw t1 num2 add t2 t0 t1 sub t3 t0 t1 sw t3 result1 sw t4 result2 end execution of the program li v0 10 syscall A bug in SPIM requires you to have an extra carriage return after the last line of code PCSpim for Windows Tutorial PCSpim for Windows is an emulator for the MIPS instruction set You can download it from the following URL ftp ftp cs wisc edu pub spim You should get the spimwin exe file from that location SPIM allows you to run simple programs written in the MIPS assembly language Your program can interact with the user with an emulated command prompt the console While your program is running you can examine the state of the emulator including the data storage and the program being run A local SPIM PCSPIM tutorial page is available at http users ece gatech edu sudha 2030 temp spim isa spim isa html Check the link to the tutorial page Note that SPIM doesn t have a built in text editor so you ll have to use Notepad or some other editor to create your assembly files Assembly files are saved as plain text files with a s file extension e g lab s Each line of the file is either a comment an instruction to the emulator or a MIPS assembly instruction When a program is read in it is divided into data and program code The memory model used by the SPIM emulator has a text segment where your program goes a data segment where declared variables are and a kernel The kernel code imitates the functions that an operating system would normally provide you should never have to do anything with it Interaction between your emulated program and a user is accomplished with a window in SPIM called the console window Special functions are provided for screen input and output MENUs in PCSpim Note the menus have more options than the ones listed here These are the options you ll probably use most often Feel free to play with the others FILE open This loads an assembly source code file a s file and prepares the emulator to run it The program will be put in the text segment and the data declarations will be put in the data segment If you get an error window when you open your s file try opening the settings and turn off the loading of the trap file If the message windows appears with syntax errors listed in it you ll have to correct your assembly code using Notepad or another editor and then try to open the file again exit Closes SPIM SIMULATOR reload Restarts the simulator and re reads assembly file you have open Use this if you run your program make changes to it in your editor and want to run it again to see if the changes worked Note that SPIM can sometimes get confused and reloading won t fix it In these cases close SPIM completely and restart it go Starts running the program It lets you choose what you want the program counter to start at i e it lets you choose which line of code to start running at Your program always begins at 0x00400000 the beginning of the text segment break This stops the assembly program wherever it might be You can look at what values are held in data memory the registers and you can see what line of code was being executed This is useful when you are debugging especially if you think you are getting stuck in an infinite loop single step Run next instruction only then break Use this to watch register and data values change as your program runs and to see which instructions are being run You can run a single step after breaking or to start the program at the first instruction 0x00400000 set breakpoints This is yet another debugging trick Suppose you are suspicious of a certain section of your program and want to watch it run Open your assembly file and look at the text segment Find the instructions you want to watch in the text segment Click on Simulator then Set Breakpoints and enter the address of the instruction that begins the portion of code you want to watch Now when you run your program SPIM will automatically break for you when it reaches that section of code WINDOW messages This shows SPIM feedback such as syntax errors when you load your program text segment This contains the program that is stored on the MIPS machine The columns in this window are the following the address of the instruction the binary for the machine code of this instruction the actual instruction being used and finally the line from your assembly file that you typed in to