1. EDUSAT SESSION FOR ADVANCED MICROPROCESSOR (EC54) Date: 08.11.2005 Session VII Topic: Programming Examples Faculty: Anita Kanavalli MSRIT

2. Program 9 Write a program to compute factorial of a positive number using recursive procedure Program.MODEL SMALL.STACK 64H.DATA Num DW 04H Fact DW ?

3. Program 9.CODE MOV AX,@DATA MOV DS,AX MOV BX,Num CALL FACT MOV AH,4CH INT 21H.EXIT

4. Program 9 FACT PROC CMP BX,00H JE Next PUSH BX DEC BX CALL FACT POP BX MUL BX

5. Program 9 RET Next: MOV AX,01H RET ENDP END

6. Interfacing PPI or Multi Function Devices (MFD) D- BF FN1 SW Register F0 F1 F2 FN2 CW Register I/O CPUCPU System Bus

7. Interfacing D-Buf is the data buffer System Bus- carries ADDR,DATA,CONTROL FN1,FN2,FN3,F0,F1….. Are functional circuits (MFC) MFC’s could be I/O ports, Timers, Transmitters, Receivers etc MFC- Independent function Each MFC has UNIQUE ADDRESS SW Register- Status register

8. Interfacing SW register- could be absent as in 8255A CW register- must be present in all MFDs ( PPIs) There could be more than one CW register Each SW and CW also has UNIQUE ADDRESS CW- defines (prepares) a functional unit in one of the modes SW- tells the status of various functional devices

9. Interfacing PROGRAMMING ? SEND CONTROL WORD / WORDS SEND/RECEIVE DATA TO/FROM each functional unit

10. Interfacing I/O s Logic Controllers Modem Stepper Motor Key board Display One for each functional unit sometimes

11. Interfacing Examples 1: Generate a square wave on PC0 pin of 8255 in the add on card Command Word of 8255 7 6 5 4 3 2 1 0 1 MD MD PA PCU MD PB PCL

12. Interfacing Examples PPI or Multi Function Devices (MFD) 8255A D- BF FN1 PA PB PC FN2 CW Register Card CPUCPU System Bus

13. Interfacing Example Program.MODEL SMALL.DATA PA EQU 200H PB EQU 201H PC EQU 202H CW WQU 203H

14. Interfacing Example.CODE MOV AX,@DATA MOV DS,AX MOV AL,80H; CW MOV DX,CW; the addr of CW moved to DX OUT DX,AL; CW sent to MFD Back: MOV AL,00H

15. Interfacing Example MOV DX,PC; move addr of port c OUT DX,AL CALL Delay; procedure call MOV AL,01H MOV DX,PC OUT DX,AL CALL Delay JMP Back

16. Interfacing Example Delay PROC MOV CX,0FFFFH Here:LOOP Here RET ENDP END

17. Interfacing Example 2: Interface a stepper motor and write program to rotate in clock- wise direction by N-steps 8255A P C 0- 3 Stepper Motor CPU Memory To all coils of the motor

18. Interfacing Example Program.MODEL SMALL.DATA PA EQU 200H PB EQU 201H PC EQU 202H CW WQU 203H

19. Interfacing Example.CODE MOV AX,@DATA MOV DS,AX MOV AL,80H; CW MOV DX,CW; the addr of CW moved to DX OUT DX,AL; CW sent to MFD MOV CX,64H; for the steps of rotation

20. Interfacing Example MOV AL,88H; data to be sent on PC lines MOV DX,PC; load DX with addr of PC Back:OUT DX,AL CALL Delay ROR AL,01H LOOP Back.EXIT

21. Interfacing Example Delay PROC …… RET ENDP END

22. Interfacing Example 3: Interface a 8X3 matrix key pad and write a program to identify the key closed.MODEL SMALL.DATA PA EQU 200H PB EQU 201H PC EQU 202H CW WQU 203H

23. Interfacing Example.CODE MOV AX,@DATA MOV DS,AX MOV AL,90H; CW MOV DX,CW; move addr of CW to DX OUT DX,AL; CW sent to MFD MOV AX,07H MOV DX,PC

24. Interfacing Example OUT DX,AL W1:MOV DX,PA IN AL,DX CMP AL,00H JZ W1 L1:MOV AH,AL MOV DX,PC OUT DX,AL

25. Interfacing Example MOV DX,PA IN AL,DX CMP AL,00H JNZ C1 ADD BL,08H MOV AL,0AH RCL AL,01H JMP L1

26. Interfacing Example C1:RCR AL,01H JC L2 INC BL JMP C1 L2:MOV BL,AL CMP AL,0AH JB Num ADD AL,07H

27. Interfacing Example Num:ADD AL,30H MOV DL,AL MOV AH,02H INT 21H MOV AH,4CH INT 21H END