Assignment
Exercise 1
• Answer these questions:
(a) How does the ALU know which function to perform?
(b) Explain clearly how the fetch-decode-execute cycle works. (What are its steps? Explain each step)
(c) Why is it that if MARIE has 4K words of main memory, addresses must have 12 bits?
(d) What is an opcode?
(e) Explain the functions of all of MARIE's registers.
(f) Explain each step the the MARIE instruction STORE performs.
(g) Describe how an interrupt works and name four different types.
Exercise 2
A digital computer has a memory unit with 24 bits per word. The instructions set consists of 150 different operations. All instructions have an operation code part (opcode) and an address part (allowing for only one address). Each instruction is stored in one word memory.
a) how many bits are needed for the opcode?
b) how many bits are left for the address part of the instruction?
c) what is the maximum allowable size for memory?
d) what is the largest unsigned binary number that can be accommodated in one word memory?
Exercise 3
A digital computer has a memory unit with 32 bits per word. The instruction set consists of 110 different operations. All instructions have an operation code part (opcode) and two address fields: one for a memory address and one for a register address. This particular system includes eight general-purpose, user-addressable registers. Registers may be loaded directly from memory and memory may be updated directly from the registers. Direct memory-to-memory data movement operations are not supported. Each instruction is stored in one word of memory.
a) how many bits are needed for the opcode?
b) how many bits are needed to specify the register?
c) how many bits are left for the memory address part of the instruction?
d) what is the maximum allowable size for memory?
e) what is the largest unsigned binary number that can be accommodated in one word of memory?
Exercise 4
Consider the MARIE program below.
a) list the hexadecimal code for each instruction.
b) draw the symbol table.
c) what is the value stored in the AC when the program terminates?
hex address label instructions
100 start, LOAD A
101 ADD B
102 STORE D
103 CLEAR
104 OUTPUT
105 ADDI D
106 STORE B
107 HALT
108 A, HEX 00FC
109 B, 14-Dec
10A C, HEX 0108
10B D, HEX 0000
Exercise 5
Consider the MARIE program below.
a) list the hexadecimal code for each instruction.
b) draw the symbol table.
c) what is the value stored in the AC when the program terminates?
hex address label instructions
200 begin, LOAD base
201 ADD Offs
202 loop, SUBT One
203 STORE Addr
204 SKIPCOND 800
205 JUMP Done
206 JUMPI Addr
207 CLEAR
208 done, HALT
209 base, HEX 200
20A Offs, 9-Dec
20B One, HEX 0001
20C Addr, HEX 0000
Exercise 6
Write the following code segment in MARIE's assembly language:
If x>1 then
Y=x+x;
X=0;
Endif;
Y=y+1;
Exercise 7
If x<=y then
Y=y+1;
Else if x !=z
Then y=y-1;
Else z=z+1;
Exercises 8
For guidance, look at Exercises 1 a & B and their solutions on page 835.
SHOW YOUR INTERMEDIATE COLUMNS that lead you to the final column solution.
Construct a truth table for:
a) xyz + x(yz)' + x'(y + z) + (xyz)'
b) (x + y') (x' + z') (y' + z')
Exercise 9
Is the fallowing true or false? Prove your answer.
(x XOR y)' = xy + (x + y)'
Exercises 10
Show that x = xy + xy'
a) using truth tables
b) Using Boolean identities
Exercise 11
Show that xz = (x + y) (x + y') (x' + z)
a) Using truth table
b) Using Boolean identities
Exercise 12
Use any method to prove the fallowing either true or false.
xz + x'y' + y'z' = xz + y'
Exercise 13
The truth table for a Boolean expression is shown below. Write the Boolean expression in sum of products form. (table is depicted below)
|
x
|
y
|
z
|
F
|
|
0
|
0
|
0
|
1
|
|
0
|
0
|
1
|
1
|
|
0
|
1
|
0
|
1
|
|
0
|
1
|
1
|
0
|
|
1
|
0
|
0
|
1
|
|
1
|
0
|
1
|
1
|
|
1
|
1
|
0
|
0
|
|
1
|
1
|
1
|
0
|
Exercise 14
Answer it and show the Truth Table for the one you selected.
Which of the fallowing Boolean expressions is not logically equivalent to all the rest?
a) wx' + xy' + xz
b) w + x' + y' + z
c) w(x' + y' + z)
d) wx'yz' + wx'y' + xy'y' + wz
Exercise 15
Given the Truth Table for (xz) + y'
state its Sum of Products expression
then draw the Logic Circuit for that Sum of Products.
xz + x'y' + y'z' = xz + y'
Exercise 16
Find the truth table that describe the following circuit:
Exercise 17
Find the truth table that describe the following circuit:
