Presentation slide

1. WELCOME TO OUR
PRESENTATION

2. Microprocessor and
Assembly Language
Programming

3. TEAM :ABRACADABRA
1. Afnanul Hassan #161-15-
7213
2. Khaled Akram Sany #161-15-
7203
3.Shami Al Rahad #161-15-
7349
4. Md. Sohanur Rahman Sakib #161-

4. WHAT IS MICROCOMPUTER?
• System Bus
Microproc
essor ROM RAM input output
Memory
Element
I/O unit

5. THE MICROPROCESSOR AND ITS
ARCHITECTURE
•ALU (Arithmetic and Logic Unit)
•The Control Unit
•Registers
HDD
RAM
Cache
Memory
Microprocessor
R1 R1
R3

6. THE PROGRAMMING
MODEL
•Program visible registers
•We can access via programs
•Program invisible registers
•We can not access via
programs

7. REGISTERS
16 bit Segment registers

8. EXAMPLE DATA
• If AX = 20A2H then AH = 20H, AL = A2H
• In other words, if AH = 1CH and AL = A2H then AX =
1CA2H
0010 0000 1010 0010
AH AL
AX

9. 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

10. 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
10101010
11101010
111010100 C = 1, in this case

11. 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
10101010 10101011
P = 1 P = 0
Even number of ones Odd number of ones
Definition changes from microprocessor to microprocessor

12. THE FLAGS
• Zero Flag – Z
• 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

13. THE FLAGS
• Trap Flag – T
• 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)

14. 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 (-32768 to 32767)

15. SIGNED VS. UNSIGNED OVERFLOW
• Let, AX = FFFFh, BX = 0001h and execute
• ADD AX, BX
1111 1111 1111 1111
+ 0000 0000 0000 0001
1 0000 0000 0000 0000
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

16. 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/XCH
G
• ADD/SUB
• INC/DEC
• NEG
None
All
All except C
All (C = 1 unless result is 0)

17. EXAMPLE 1
• Let AX = FFFFh, BX = FFFFh and execute ADD
AX, BX FFFFh
+ FFFFh
1 FFFEh
The result stored in AX is FFFEh = 1111 1111 1111 1110
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

18. EXAMPLE 2
• Let AX = 8000h, BX = 0001h and execute SUB
AX, BX 8000h
- 0001h
7FFFh
The result stored in AX is 7FFFh = 0111 1111 1111 1111
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

19. SEGMENT REGISTERS
16 bit Segment registers
*
*
*
Segment 1
Segment 2
Segment n
0000hCS
8000hDS
A000hSS
Fig:The programming model of intel 8086 trough the Pentium pro