Basic Assembly Language Programming Examples for Microcontrollers

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Microcontroller Assembly Language Programming

1. Write a program to implement the logical function “P1.4 = P1.0 ∨ (P1.1 ∧ P1.2) ∨ P1.3” using bit manipulation instructions.

MOV C,P1.1
ANL C,P1.2
ORL C,P1.0
ORL C,P1.3
MOV P1.4,C

2. Write a program that jumps to the LABLE storage unit if the content of accumulator A meets the following conditions. Assume A contains an unsigned number.

(1) A ≥ 10; (2) A > 10; (3) A ≤ 10.

(1)

CJNE A,#10,NEXT
LJMP LABLE
NEXT:
JNC LABLE

(2)

CJNE A,#10,NEXT
LJMP NEXT2
NEXT:
JNC LABLE
NEXT2:

(3)

CJNE A,#10,NEXT
LJMP LABLE
NEXT:
JC LABLE

3. Write a program to check if the data 55H exists in the internal RAM units from 30H to 50H. If found, set the 51H unit to FFH; if not found, clear the 51H unit to 0.

MOV R0,29H
NEXT:
INC R0
CJNE R0,#51H,NEXT2
MOV 51H,#0FFH
AJMP OVER
NEXT2:
CJNE @R0,#55H,NEXT
MOV 51H,#0
OVER:

4. Write a program to count the number of occurrences of 0 in the internal RAM units from 30H to 50H, and store the result in the 51H unit.

MOV R0,30H
MOV 51H,#0
NEXT:
CJNE @R0,#00H,NEXT2
INC 51H
NEXT2:
INC R0
CJNE R0,#51H,NEXT

5. There is a data block in external RAM containing several characters and numbers, starting at address SOURCE. Transfer this data block to the internal RAM area starting at DIST, stopping when the character “$” is encountered (the “$” should also be transferred, its ASCII code is 24H).

MOV DPTR,#SOURCE
MOV R0,#DIST
NEXT:
MOVX A,@DPTR
MOV @R0,A
INC DPTR
INC R0
CJNE A,#24H,NEXT

6. The internal RAM units 30H and 31H store a 16-bit binary number, with the high byte first and the low byte last. Write a program to compute its complement and store it back in the original location.

CLR C
MOV A,#0
SUBB A,31H
MOV 31H,A
MOV A,#0
SUBB A,30H
MOV 30H,A

7. There are two 4-byte compressed BCD numbers stored in the internal RAM, one in units 30H–33H and the other in units 40H–43H. Write a program to add them, storing the result in BCD format in units 30H–33H.

CLR C
MOV R0,#30H
MOV R1,#40H
MOV R2,#4
NEXT:
MOV A,@R0
ADDC A,@R1
MOV @R0,A
INC R0
INC R1
DJNZ R2,NEXT

8. Write a program to transfer 16 bytes of data stored in external RAM starting from 2000H to the internal RAM starting from 30H.

MOV DPTR,#2000H
MOV R0,#30H
MOV R1,#0
NEXT:
MOVX A,@DPTR
MOV @R0,A
INC DPTR
INC R0
INC R1
CJNE R1,#16H,NEXT

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