1
Lab 5
Embedded MIPS Core Programming
Jacobi Zakrzewski
Andrew Healy
11/22/2009
Grading Points
Item
Points Possible
Title page, Table of Contents,
Introduction
5
Software Design and
Documentation (see attached)
10
Demonstrations
30
Conclusions
5
Appendices: VHDL code, MIPS
Assembly code.
10
Effort and Quality
5
Total
65
2
Table of Contents
1—Title Page
2—Index
3—Introduction, Design Description
4—Design Description, VHDL Code
5—Conclusion, Appendices
6—Appendices
3
Introduction
The purpose of lab 5 was to program a small microprocessor into VHDL. With that goal in mind, we had
to use our Spartan 3E board, Xilinx Project Navigator, and code taken off of eLearn. In order for our
project to work correctly we had to add to and modify the code already given to us. The first part of the
lab was to implement the design already given to us, after that we were to modify the code in order to
complete the objective of reading in a value, entering it, read in another value, enter that, and add the
two previous numbers. The sum should display on the 8 LEDS.
Design Description
Our design started off with all the files taken off of eLearn, all of this had included constraints and
coding that dealt with the counter on the seven-segment display and the rotary switch. We had to add a
few things to this in order for our lab to be completed though. First we started a new project in Xilinx
Project Manager, integrated all the files given to us on eLearn. The program didn’t work out of the box
and we had to create a file called RegisterFile.vhdl, take more code off of eLearn, and implement that
into the new file. Finally, we synthesized, implement design, and generated a programming file. We
hooked up the Spartan 3E board and used iMPACT in order for the hardware to talk to each other. After
that was all said and done, we tested the board and our rotary switch displayed hexadecimal digits on
the seven-segment display. Now we just had to begin part two.
Part two we were to read two inputs from two different locations on the board, add them, and store the
result. Simply put, we were to use the rotary switch to enter in the two numbers, press it down each
time you enter a number, and then display the result on the 8 LEDS. To start this process we took an
example from the file ‘ifetch.vhld’ and modified it to adhere to our objective. We then wrote the
program in MIPster, including memory locations for two numbers, an addition, and a result. We had to
use specific locations for the two numbers entered (0XC004 and 0XC000) because that is where the
4
binary and push buttons are stored. We then ran it through PCSpim, and copied down the instructions
to put into our VHDL program. After that we recompiled our VHDL project and implemented it onto our
Spartan 3E board. We ran our program and were able to add two hexadecimal numbers from our rotary
switch, add them and have it display on the 8 LEDS.
VHDL Code:
##########################################################################
###########################
#Programmer(s) name(s): Jacobi Zakrzewski, Andrew Healy
#Date last modified: 11/20/2009
#File Name: Lab_05_JZ_Ah.s
#Description of contents: This program will store, and add two #different
locations from the board, and then store the result #back into a location.
#Then it loops back infinitely
##########################################################################
############################
.data # Data declaration section
.text
#############################################################
# Main:
Read two integers from two locations on the board, #add them
and store them back in the first location
# Inputs:
0XC004: rotary switch used to input number
#
0XC000: Binary counter used to input number
# Outputs: 0XC000: Result from adding the 2 numbers is stored here
#############################################################
main:
# Start of
li $t1, 0xC004
li $t2, 0xC000
lw $t1, 0($a0)
lw $t2, 0($a1)
add $t1, $t1, $t2
sw $t1, 0xC000
(0Xc000)
beq $zero, $zero, main
# END OF PROGRAM
code section
#load number into t1 from 0XC004
#load second number into t2 from 0XC000
#load number into t1 from a0
#load number into t2 from a1
#add t1 and t1, store back in t1
#store result in t1, as well as address on board
#branch, loop infinitely
5
Conclusion
From this, we learned how to convert assembly language to something VHDL will recognize. To do this
we started a new project in Xilinx, implemented many files from eLearn, analyzed the code given to us,
and modified that code in order to complete our objective. We had to convert from assembly to
something VHDL would recognize by writing a program in MIPster, and taking those instructions over to
VHDL. This process was quick, but took a lot of integrating and transferring of code/files in order for it
to work.
Appendices
Assembly used to add two inputted numbers, stored
##########################################################################
###########################
#Programmer(s) name(s): Jacobi Zakrzewski, Andrew Healy
#Date last modified: 11/20/2009
#File Name: Lab_05_JZ_Ah.s
#Description of contents: This program will store, and add two #different
locations from the board, and then store the result #back into a location.
#Then it loops back infinitely
##########################################################################
############################
.data # Data declaration section
.text
#############################################################
# Main:
Read two integers from two locations on the board, #add them
and store them back in the first location
# Inputs:
0XC004: rotary switch used to input number
#
0XC000: Binary counter used to input number
# Outputs: 0XC000: Result from adding the 2 numbers is stored here
#############################################################
main:
# Start of
li $t1, 0xC004
li $t2, 0xC000
lw $t1, 0($a0)
lw $t2, 0($a1)
add $t1, $t1, $t2
sw $t1, 0xC000
(0Xc000)
beq $zero, $zero, main
# END OF PROGRAM
code section
#load number into t1 from 0XC004
#load second number into t2 from 0XC000
#load number into t1 from a0
#load number into t2 from a1
#add t1 and t1, store back in t1
#store result in t1, as well as address on board
#branch, loop infinitely
6
Modified ifetch.vhdl
X"3404c004",
X"3405c000",
X"8c890000",
X"8caa0000",
X"012a4820",
X"ac09c000",
X"1000fffb",
--------
ori $4, $0, -16380
; 2: li $t1, 0xC004
ori $5, $0, -16384
; 3: li $t2, 0xC000
lw $9, 0($4)
; 4: lw $t1, 0($a0)
lw $10, 0($5)
; 5: lw $t2, 0($a1)
add $9, $9, $10
; 6: add $t1, $t1, $t2
sw $9, -16384($0)
; 6: sw $t1, 0xC000
beq $0, $0, -20 [main-0x00400038]; 7: beq $zero, $zero, main
RegisterFile.vhdl
library IEEE;
use IEEE.STD_LOGIC_1164.all;
USE IEEE.STD_LOGIC_ARITH.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
USE IEEE.numeric_std.ALL;
entity RegisterFile is -- three-port register file
generic(datapath_size : integer);
port(clk:
in STD_LOGIC;
we3:
in STD_LOGIC;
ra1, ra2, wa3: in STD_LOGIC_VECTOR(4 downto 0);
wd3:
in STD_LOGIC_VECTOR(datapath_size - 1 downto 0);
rd1, rd2:
out STD_LOGIC_VECTOR(datapath_size - 1 downto 0));
end RegisterFile;
architecture Behavioral of RegisterFile is
type ramtype is array (31 downto 0) of STD_LOGIC_VECTOR(datapath_size - 1 downto 0);
signal mem: ramtype;
begin
-- three-ported register file
-- read two ports combinationally
-- write third port on rising edge of clock
process(clk) begin
if (clk'event and clk = '1') then
if we3 = '1' then mem(CONV_INTEGER(wa3)) <= wd3;
end if;
end if;
end process;
rd1 <= conv_std_logic_vector(0,datapath_size) when (conv_integer(ra1) = 0) -- register 0 holds 0
else mem(CONV_INTEGER(ra1));
rd2 <= conv_std_logic_vector(0,datapath_size) when (conv_integer(ra2) = 0) -- register 0 holds 0 else
mem(CONV_INTEGER(ra2));
end;