CS-220, Sections 50, 51
Laboratory Exercise # 1
2-2-06, Report Due Date: 2-9-06
In this lab you will be doing some work with a program that simulates the simple
computer with a hardwired control unit that we are discussing in class. I will be
sending the simulator program to the CS-220 listserv and you should save a copy
of it on the hard disk of the computer you are using in the lab. (If you have
your own PC, you may want to put the simulator program on that machine as well so
you can work with it at home. If you do so, please be advised that you will need
to have the Microsoft .NET Framework installed on your machine. If you have
Visual Studio .NET installed, the Framework will already be there.) The lab
instructor will also have a copy of the program executable on a floppy disk,
Flash drive, or CD-ROM so that if you did not receive the email to the listserv
you can upload it from the lab instructor's disk.
Description of the Simulator
The simulator simulates execution of programs on the computer described in the
Week 2 class notes at http://www.cs.binghamton.edu/~reckert/220/hardwire3new.html.
You should have a copy of those notes with you in lab. When you start the
simulator, something like the following appears on the screen:
Note that there are two windows: one on the left representing the data path section
of the simple computer and the other one representing its hardwired control unit.
The user may take any of the following actions by pressing the appropriate button in
the upper right-hand corner of the data path window: Load or change a machine language
program in the computer's RAM memory, Load a predefined example program into RAM,
start the clock (in which case the fetch-decode-execute cycle will begin, causing
whatever program is currently in RAM to be executed until a HLT (opcode 8) instruction
is fetched and executed), stop the clock, single step through the program (causing the
next clock pulse to be issued), or reset the registers of the computer to their
initial values.
Each time a new clock pulse is issued while the clock is running or when the single
step button is pressed, all of the data path's active control signals are displayed;
the busses and registers that are currently being used at that moment are highlighted
in red and their contents displayed; the action that has occurred is indicated; the
new contents of the registers and memory are displayed; and the appropriate active
control lines inside the hardwired controller are highlighted in red.
When the user presses the "Load or Change RAM" button, the following dialog box is
displayed:
The address field is preset to 00 and automatically increments by one every time
the user enters a new value into the "Contents" box. Data are entered into the
"Contents" box by typing a three digit decimal integer there that can be either a
machine language instruction or a data value to be stored at the current address in
RAM. The number is stored in RAM when the user clicks the "Enter Contents" button.
If the user wants to change the contents of some RAM word other than the one at the
current address, he or she must enter the desired address into the "Address" box,
click the "Change Address" button, then enter the desired three-digit number into
the "Contents" box, and finally click on the "Enter Contents" button. After the
user is finished entering a series of numbers (e.g., a program), the changes are
stored in RAM when he or she clicks the "Done" button. The values will be updated
in the RAM listbox in the data path section. This action also dismisses the dialog
box. The "Load Memory Dialog Box" may be called up at any time, either to enter a
new program or to change the current program.
Part 1 -- Using the Simulator with the Example Program
A. Press the "Load Example Program" button. Make a table like the following in
which you indicate the address and contents of each RAM memory address. For each
address, on the right-hand side of the table write down an assembly language
statement that is equivalent to the machine language instruction or pseudo-op
stored at that address. If there are any jump statements, be sure to make up label
names and place them at the right place in the assembly language statement. The
first statement has been done for you:
Machine Language Assembly Language
Address Contents Label Operation Operand
00 108 LDA 08
B. Single step the simulator through the program. Make another table that shows the
active control signals and the contents of all registers after each clock pulse.
This should be something like the following. (Again the first one has been done for
you.)
Clock PC MAR MDR ACC ALU NF B IR Ring Active RAM Address
Pulse Count Signals Being Accessed
0 0 0 0 0 0 0 0 0 0 EP,LM 00
1
2
3
4
5
6
etc.
C. The figure below is a diagram of the simple computer's hard-wired control unit.
Make 12 copies of this diagram. You are to highlight with a colored highlighter all
signal lines, AND gates, OR gates, and flip-flops that are active (are high), as well
as write in the values that are contained in the Instruction Register, the Negative
Flag, and the "Active Control Signals" boxes in one of these diagrams at each of the
following moments in the execution of the example program:
Ring Pulse 0 of the first "fetch" of the second instruction in the program
Ring Pulse 2 of the first "fetch" of the third instruction in the program
Ring pulse 5 of the instruction stored at address 00, the first time it is executed
Ring pulse 3 of the instruction stored at address 03, the first time it is executed
Ring pulse 4 of the instruction stored at address 03, the second time it is executed
Ring pulse 5 of the instruction stored at address 04, the first time it is executed
Ring pulse 3 of the instruction stored at address 05, the first time it is executed
Ring pulse 0 of the following fetch
Ring pulse 3 of the instruction stored at address 06, the first time it is executed
Ring pulse 0 of the following fetch
Ring pulse 3 of the instruction stored at address 05, the second time it is executed
Ring pulse 0 of the following fetch
In each case describe exactly what is occurring at that moment in the data path
section including any changes in the contents of registers, RAM, or the negative flag.
(For example, for Ring Pulse 0 of the fetch of the first instruction, the answer
would be something like: "the 0 in the PC is being copied over the bus to the MAR,
thus accessing the 108 stored at address 00 in RAM".)
Part 2. Writing some Programs and Executing them on the Simulator
A. Write an assembly language program targeted for this computer that adds and
subtracts the numbers stored at RAM addresses 10 and 11, storing the results in
addresses 12 and 13. Hand assemble (translate) the program into machine language
and include both the assembly language and the machine language translation (the
hand-assembled listing) in your lab report. Use the format of the table at the
beginning of Part 1A of this handout. Enter your program and two data values
(for example 8 and 3) into the simulator and single step through it. Show a
working simulator run of your program to the lab instructor. How many clock
pulses are issued during the program run from the time you start the clock until
the moment the HLT instruction stops the clock?
B. Write and hand-assemble a program that multiplies two numbers stored in RAM
using a "multiply by successive additions" algorithm. The numbers to be
multiplied as well as the result should be stored in successive RAM locations.
Run your program on the simulator and, when it is working properly, show a
simulator run to the lab instructor. Use the numbers 5 and 3 (result should be
15). How many clock pulses are issued during the program run from the time you
start the clock until the moment the HLT instruction stops the clock? Change the
numbers to be multiplied and run the simulator again, showing it to the lab
instructor. Be sure to submit the hand-assembled listing of the program with
your report.
C. Write and hand-assemble a program that computes the following:
z = (x+y-w)*u/v
Here u, v, w, x, and y will all be variables (memory locations) in the data
section of your program. The result of the computations should be stored in
another RAM location called z. You will need to use your "multiply by
successive additions" algorithm from Part B and create a "divide by successive
subtractions" algorithm in order to write this program. As in Part B, run the
program on the simulator and show the run to the lab instructor. Use the
following data: x=3, y=6, w=5, u=3, v=2. (The result should be 6). How many
clock pulses does it use to run to completion? Run it again with other data
values. Be sure to submit the hand-assembled listing of the program with your
report.