BAi 1 Thiet ke card giao dien 8255 su dung dia chi 3CFh.

Viet chuong trinh xu li du lieu nhap vao tu PA,PB

D(PA) = 2D(PB) thi tong hai du lieu chuyen ra PC

D(PA) > 2D(PB) ------------------------------ PB

D(PA) < 2D(PB) ------------------------------ PA

- Xac dinh dia chi: 3CFh= 0011 1100 1111

ta co A1A0 = 11 suy ra 3CFh la dia chi cua CWR

3CEh -------------- PC

3CDh -------------- PB

3CCh -------------- PA

- Xac dinh tu dieu khien: 1 0 0 A CA 0 B CB

* PA=PB=I,Pc=O ta co 1 0 0 1 0 0 1 0 --> CW1 = 92h

* PB=PC=I,PA=O ta co 1 0 0 0 1 0 1 1 --> CW2 = 8Bh

* PA=PC=I,PB=O ta co 1 0 0 1 1 0 0 1 --> CW3 = 99h

-Chuong trinh:

* Model Small

* Stack 100

* Data

PA EQU 3CCh

PB EQU 3CDh

PC EQU 3CEh

CWR EQU 3CFh

CW1 EQU 92h

CW2 EQU 8Bh

CW3 EQU 99h

*Code

Main proc

MOV AX,@Data

MOV DS,AX

MOV AL,CW1; truong hop PA=PB=I, PC=O

OUT CWR,AL

IN AX,PB; dua D(PB) vao BX

MOV BX,AX

IN AX,PA; dua D(PA) vao AX

MOV DX,BX ; dua D(PB) vao DX de xu li tiep, giu lai BX

SHL DX,1; nhan doi D(PB) luu vao DX

MOV CX,AX; dua D(PA) vao CX de xu li tiep

CMP CX,DX; so sanh D(PA) voi 2D(PB)

JE bang; D(PA)=2D(PB)

JG lon; D(PA)>2D(PB)

JL nho; D(PA)<2D(PB)

bang: ADD CX,BX; tong luu vao CX

MOV AX,CX

OUT PC,AX

JMP Exit

lon: MOV AL,CW3; PB=O

OUT CWR,AL

ADD CX,BX; tong luu vao CX

MOV AX,CX

OUT PB,AX

JMP Exit

nho: MOV AL,CW2; PC=O

OUT CWR,AL

ADD CX,BX; tong luu vao CX

MOV AX,CX

OUT PA,AX

Exit: MOV AH,4Ch

INT 21h

MAIN Endp

END MAIN