1. Presented By Dr. Shazzad Hosain Asst. Prof. EECS, NSU
CSE 331/ETE 332/EEE 332 Microprocessor and Assembly Language Programming
Presented By
Dr. Shazzad Hosain
Asst. Prof. EECS, NSU

2. Books
Fundamentals of Digital Logic and Microcomputer Design – M. Rafiaquzzaman
The Intel Microprocessors 8086/8088 … , and Pentium Pro Processors – Barry B. Brey
Assembly Language Programming and Organization of the IBM PC – Ytha Yu, Charles Marut

3. Mark Distribution Best 3 out of 5 Items Percentage Attendance 5%
Quizzes
25%
Mid Term
Lab
10%
Final
35%
Total
100%
Best 3 out of 5
There will be no makeup for quizzes or exams. For details please visit
and follow the corresponding link.

4. Assembly Language Programming

5. What is Microcomputer?

6. The Microprocessor and Its Architecture
ALU (Arithmetic and Logic Unit)
The Control Unit
Registers
HDD
RAM
Cache Memory
Microprocessor R1 R3

7. The Programming Model Program visible registers
We can access via programs
Program invisible registers
We can not access via programs

8. Registers
16 bit Segment registers

9. Example Data If AX = 20A2H then AH = 20H, AL = A2H
In other words, if AH = 1CH and AL = A2H then AX = 1CA2H AH AL AX

10. The FLAGS register FLAGS indicate the condition of the MP
Also control the operations
FLAGS are upward compatible from 8086/8088 to Pentium/Pentium Pro
Figure 2.2: The EFLAG and FLAG registers

11. The FLAGs
Carry Flag – C
C = 1 if there is a carry out from the msb on addition
Or, there is a borrow into the msb on subtraction
Otherwise C = 0
C flag is also affected by shift and rotate instructions
C = 1, in this case

12. The FLAGs Parity Flag – P
P = 1 for even parity, if number contains even number of ones
P = 0 for odd parity, if odd number of ones
Even number of ones
Odd number of ones
P = 0
P = 1
Definition changes from microprocessor to microprocessor

13. The FLAGs Zero Flag – Z Sign Flag – S Z = 1 for zero result
Z = 0 for non-zero result
Sign Flag – S
S = 1 if msb of a result is 1, means negative number
S = 0 if msb of a result is 0, means positive number

14. The FLAGs Trap Flag – T Direction Flag – D
Enables trapping through an on-chip debugging feature
T = 1 MP interrupts the flow of a program, i.e. debug mode is enabled
T = 0 debug mode is disabled
Direction Flag – D
Selects increment/decrement mode of SI and/or DI registers during string instructions
D = 1, decrement mode, STD (set direction) instruction used
D = 0, increment mode, CLD (clear direction) instruction used

15. The FLAGs Overflow Flag – O O = 1 if signed overflow occurred
O = 0 otherwise
Overflow is associated with the fact of range of numbers represented in a computer
8 bit unsigned number range (0 to 255)
8 bit signed number range (-128 to 127)
16 bit unsigned number range (0 to 65535)
16 bit signed number range ( to 32767)

16. Signed vs. Unsigned Overflow
Let, AX = FFFFh, BX = 0001h and execute
ADD AX, BX AX BX
Unsigned interpretation
Correct answer is 10000h = 65536
But this is out of range.
1 is carried out of msb, AX = 0000h, which is wrong
Unsigned overflow occured
Signed interpretation
FFFFh = -1, 0001h = 1, summation is -1+1 = 0
Singned overflow did not occur

17. How instructions affect the flags?
Every time the processor executes a instruction, the flags are altered to reflect the result
Let us take the following flags and instructions
Sign Flag – S
Parity Flag – P
Zero Flag – Z
Carry Flag – C
MOV/XCHG
ADD/SUB
INC/DEC
NEG
None
All
All except C
All (C = 1 unless result is 0)

18. Example 1 Let AX = FFFFh, BX = FFFFh and execute ADD AX, BX S P Z C
1 FFFEh
The result stored in AX is FFFEh = S P Z C
= 1 because the msb is 1
= 0 because the are 15 of 1 bits, odd parity
= 0 because the result is non-zero
= 1 because there is a carry out of the msb on addition

19. Example 2 Let AX = 8000h, BX = 0001h and execute SUB AX, BX S P Z C
7FFFh
The result stored in AX is 7FFFh = S P Z C
= 0 because the msb is 0
= 0 because the are 15 of 1 bits, odd parity
= 0 because the result is non-zero
= 0 because there is no carry

20. Registers
16 bit Segment registers

21. Segment Registers Segment n * SS A000h Segment 2 DS 8000h Segment 1
16 bit Segment registers
0000h CS

22. An Assembly Program #include <stdio.h> void main () {
int I, j ; *********
// comment
********* }
Example 3-5 of Barry B. Brey’s book

23. An Assembly Program Cont.
AH AL
00h h AX
BH BL
AAh AAh BX
What is the content of BX?
10h
00h
AAh
DATA DATA DATA DATA4

24. Assembly Language Structure

25. An Assembly Program
SMALL model allows one data segment and one code segment
TINY model directs the assembler to assemble the program into a single segment
DB for Define Byte (one single byte)
DW for Define Word (two consecutive bytes)
10h
00h
AAh
DATA DATA DATA DATA4

26. Another Example

27. References
Ch 6, Digital Logic and Microcomputer Design – by M. Rafiquzzaman
Ch 2, Intel Microprocessors – by Brey
Ch 5, Assembly Language Programming – by Charls Marut