ECE 332
Due: 09/27/2010
Homework 5
Fall 2010
1. Use the following assembly code and memory snapshots to answer the
questions on the following page.
# file: problem7.s
# file: magic.s
.include “system.inc”
.text
.text
magic: .global magic
_start: .global _start
movia
sp,STACK
C:
movi
r17,801
srli
r17,r17,4
andi
r4,r17,0xf
call
magic
mov
r4,r2
call
prints
br
.
movia
r8,LIST
andi
slli
add
ldw
r9,r4,0xf
r9,r9,2
r9,r8,r9
r2,0(r9)
ret
.data
A:
B:
LIST:
m0:
m1:
m2:
m3:
.end
You can assume that the symbol _start is
associated with memory address 0x20000.
.word
0xaaaaaaaa
.word
m0, m1, m2, m3
.word
0xbbbbbbbb
.string
.string
.string
.string
"dragon"
"rat"
"rabbit"
"tiger"
.word
0xcccccccc
.end
Note: The data section of magic.s is loaded at
memory address 0x200e0.
Figure 7.1. Partial memory snapshot of data section (word format)
Figure 7.2. Partial memory snapshot of data section (byte format)
Page 1 of 4
ECE 332
Due: 09/27/2010
Homework 5
Fall 2010
1. Based on the code and memory snapshots on the previous page:
(answers in hex)
a. What is the value of the symbol LIST?
______________
b. What is the value of the symbol m0?
______________
c. What is the value of the symbol m1?
______________
d. What memory address is referenced by the symbol LIST?
______________
e. What memory address is referenced by the symbol m0?
______________
f.
______________
What memory address is referenced by symbol m1?
g. When the program counter (PC) is positioned to the location referenced by
symbol A, what is the value of the ra register?
______________
h. When the program counter (PC) is positioned to the location referenced by
symbol B, what is the value of the ra register?
______________
i.
When the program counter (PC) is positioned to the location referenced by
symbol C, what is the value of the ra register?
______________
j.
(7 points) What is the sequence of bytes (hex) sent to the JTAG UART
terminal?
______________
Page 2 of 4
ECE 332
Due: 09/27/2010
Homework 5
Fall 2010
Below is a screen capture from debugging a small C program. In the left pane is the C source, and on the
right is the generated assembly language code. Inspect the generated assembly instructions, and compare
them to assembly code that you have written in the past.
In particular, note the translation of the c = a + b statement:
Page 3 of 4
ECE 332
Due: 09/27/2010
Homework 5
Fall 2010
For this homework, you are asked to code specific C language statements to do some of the same things that
were done previously using assembly language. For each problem write the C language code to produce the
requested functionality, and then run the code and capture the generated assembly code as shown above. For
example, consider the following. (While you are doing this assignment, keep in mind that this is not
optimized code.)
Provided with this assignment are files that you can use as the basis for instruction set simulation using the
Nios II IDE environment. Copy the files N2SIM.ptf and N2SIM.sof to the workspace directory.
Example: Produce code that increments a variable.
Solution:
C code
Generated assembly code
int i = 4;
i++;
int i = 4;
0x00020220 <main+12>: movi r2,4
0x00020224 <main+16>: stw r2,12(fp)
i++;
0x00020228 <main+20>: ldw r2,12(fp)
0x0002022c <main+24>: addi r2,r2,1
0x00020230 <main+28>: stw r2,12(fp)
For each of the problems listed below, use the value w0 as input data to manipulate. Provide screen capture
the assembly code generated with your submittal.
int main()
{
word w0 = 0x12345677;
word w1, w2, w3, w4, w5, w6, w7, w8;
w1
w2
w3
w4
w5
w6
w7
w8
=
=
=
=
=
=
=
=
???;
???;
???;
???;
???;
???;
???;
???;
//
//
//
//
//
//
//
//
one’ complement
shift left 12 bits
shift right 16 bits
set bit 19
clear bit 18
toggle bit 12
get bits 19-16 of w0
Rotate w0 right 8 bits
return 0;
}
1.
Set w1 to the one’s complement of w0.
2.
Shift w0 left by 12 bits and assign to w2.
3.
Shift w0 right by 16 bits and assign to w3.
4.
Set bit 19 of w0 to a one and assign to w4.
5.
Clear bit 18 of w0 and assign to w5.
6.
Toggle bit 12 of w0 and assign to w6.
7.
Get bits 19-16 of w0 (move to positions 3-0) and assign to w7
8.
Rotate w0 right 8 bits and assign to w8.
Page 4 of 4