Question

Write a program to read the following numbers from ROM and place them in data RAM
starting at address 0x50. Only, the last number in ROM is zero; the rest, are non-zero. (9 points)
Org 0x600
MYDATA DB 0x12, 0x45, 0x58, ..., 0x00

Answer 1

Solution:

Concept:

• Since only the last byte is zero, we can check the end of string by checking the data byte when it is read from ROM..
• R0 is used as RAM pointer
• DPTR is used as ROM Pointer

ASM CODE:

ORG 0H   // START OF PROGRAM
MOV R0,#50H                   // POINTER FOR RAM STARTING FROM 50H
MOV DPTR,#MYDATA               // LOAD THE POINTER OF CODE DATA IN DPTR
AGAIN:
CLR A                               // CLEAR ACCUMALAOTR
MOVC A,@A+DPTR                       // GET THE DATA BYTE FROM ROM INTO ACCUMULATOR
JNZ CONT                           // IF NOT ZERO, THEN CONTINUE
LJMP STOP1                           // IF ZERO THEN WE HAVE REACHED END OF STRING, STOP THE PROG
CONT:
INC DPTR                           // INCREMENT CODE MEMORY POINTER TO POINT THE NEXT DATA BYTE
MOV @R0,A                           // COPY DATA FROM ACCUMULATOR TO RAM ADDRESS POINTED BY R0
INC R0                           // INCREMENT RAM POINTER FOR STORING NEXT DATA BYTE
SJMP AGAIN                       // REPEAT THE PROCESS

// ROM DATA BYTE STRING....END OF STRING IS MARKED BY 00H
ORG 600H
MYDATA: DB 12H, 45H, 58H, 01H, 02H, 03H, 04, 05H, 06H, 07H, 00H

STOP1:
END           // END OF PROGRAM

SCREEN SHOT: