1. Lecture 2
Programming of 8086
Лектор: Люличева И.А. 1

2. Content
Addressing modes of х86
Examples of programs
Examples of using ports

3. Universal microprocessors instruction groups
Instruction set of MP 8086 consist of 6 groups:
1. Data transfer instructions.
2. Arithmetical instructions.
3. Logical operations and shift instructions.
4. Flow control instructions.
5. Chains (arrays) instructions.
6. Microprocessor control instructions. 3

4. Addressing modes The x86 processors support
the register addressing mode ,
the immediate addressing mode,
the direct addressing mode,
implicit addressing mode,
the indirect addressing mode,
stack addressing mode,
the base plus index addressing modes,
and the base relative plus index addressing mode. 4

5. Addressing modes
Register operands are the easiest to understand. Consider the following forms of the mov instruction:
mov ax, bx or mov ax, cx
Constants are also pretty easy to deal with. Consider the following instructions:
mov ax, 1e41h or add di, 160

6. Addressing modes
Direct addressing mode to Memory we rear will use: Mov ax, [100]
But to ports it may be useful:
In al, 40h or In ax, 60h
implicit addressing mode:
STOWS, MOWSW, DAA, WIAT, NOP, LOOP
Stack addressing mode uses SS:SP pair
Instructions: Push, Pop, Call, Ret 6

7. Addressing modes the indirect addressing mode may be of 3 types
1. index – using DI or SI
Mov es:[di], ax
2. base – using BX or BP
Mov ax, ds:[bx]
3. indirect to ports
Mov dx, 3E8h
In ax, dx 7

8. Addressing modes
the base plus index addressing modes we may use for two dimensional arrays:
Mov ax, [bx+di] or add [bp+si], 2000h
Index or base relative addressing mode (with the bias) we used in laboratory work N1:
Mov ES:[DI+2000], AX 8

9. Addressing modes
Indirect addressing modes for 16-bit x86 processors can be summarized by this formula:

10. Work with chains MOV ES, AX { futher! }
Example of clear screen program
MOV AX, 0B800H { Do not repeat
MOV ES, AX { futher! }
XOR DI,DI
MOV CX, 80*25
XOR AX,AX
REP STOSW 10

11. Examples of programs
Example of using STOSB/W for filling 10th line of Pc screen by number 3.
MOV DI, 160*10 (1 -2 bytes!)
MOV CX, 80
MOV AX, 1E33Н (33Н – ASCII code for 3)
REP STOSW 11

12. Block-diagr for filling the colomn. 12 12

13. Examples of programs Example of filling the colomn by increasing code.
MOV AX, 0B800H
MOV ES, AX
XOR DI,DI
MOV CX, 25
MOV AX, 2F41H (41H – code of А)
@L1:MOV ES:[DI], AX
INC AX
ADD DI, 160 13 13

14. Microprocessor based Systems contains:
CPU (central processing unit)
Microprocessor core
Cash memory
logic circuitry for communicating with the system bus: data/address bus driver, bus controller
System memory stores both program code and data
ROM, BIOS (read-only memory), RAM (random access memory)
Timing unit
generates clock signals and is responsible for the proper operation of all system hardware
crystal oscillator and timing circuitry
Interrupt circuitry
mechanism for the processor to respond to special external events
I/O, peripherals
Dicks, monitor, keyboard, mouse, printer, …

15. Von Naiman Model of MP system15

16. Input array of data from ports

17. 8255 parallel port diagram

18. 8251 serial port block-diagram

19. 8253 timer block-diagram

20. Control words of timer

21. Examples of programs
Input array of data from port 40H and output it to the colomn at the screen.
XOR DI,DI
MOV CX, 25
@L1: IN AX, 40H {40H – address of port}
MOV ES:[DI], AX
ADD DI, 80 21

22. Examples of programs
Block-diagr for 100 times input arrays from ports with the delay.
1. Counter= (100)
2. Execute the subroutine of input array from port.
4. call delay
6. counter--
7. Counter= 0? – of NOT go to p.2 else - END. 22

23. Main menu for the debugger23

24. Changing state of registers24

25. Self-control questions
Groups of instr 8086
Far and long jumps.
Addressing modes in the example 1
Addressing modes in the programm of input data from the ports 25