8051 instruction set, addressing modes-2

MOV A, #56H

MOV R1, #50H

MOV 50H, # 45H

XCHD A, @R1

What is the result at A, R1?

• 56H, 45H

• 45H, 50H

• 50H, 56H

• 45H, 56H

Which of the following instruction is used to set bit port directly?

• SET P1.0

• MOV P1.0, bit

• SETB P1.0

• JB P1.0, bit

SP of 8051 is of ___ wide and it is loaded with the default value of ___ after reset.

• 2 byte, 08H

• 8 bit, 07H

• 1 byte, 09H

• 8 bit, 06H

Find the number of times the following loop will be executed

MOV R6,#200

BACK:MOV R5,#100

HERE:DJNZ R5, HERE

DJNZ R6,BACK

END

• 100

• 200

• 20000

• 2000

Do the two instructions mean the same?

1) BACK: DEC R0

JZ BACK

2) BACK: DJNZ RO, BACK

• yes

• no

• cant be determined

• yes and the second one is preferred

Which instruction is used to check the status of a single bit?

• MOV A,P0

• ADD A,#05H

• JNB PO.0, label

• CLR P0.05H

9. Which of the following comes under the indexed addressing mode?

• MOVX A, @DPTR

• MOVC @A+DPTR,A

• MOV A,R0

• MOV @R0,A

What does the symbol '#' represent in the instruction MOV A, #55H ?

• a. Direct datatype

• b. Indirect datatype

• c. Immediate datatype

• d. Indexed datatype

Which register usually store the output generated by ALU in several arithmetic and logical operations?

• Accumulator

• Special Function Register

• Timer Register

• Stack Pointer

How many registers can be utilized to write the programs by an effective selection of register bank in program status word (PSW)?

• 8

• 16

• 32

• 64