1) Differentiate SUBB A, B & CJNE A, B, loop. Justify your answer with the changes in the different programmable registers if [A]=01h,[B]=05h.

(ii) Identify the addressing modes of the following instructions. Explain its operation with example.

i) MOV A, @ A+ PC

(ii) CLRA

(iii) SJMP Label

(2) In an auto irrigation system, daily recorded soil moisture for 5 times a day is available in RAM memory location starting from 60H. Write an 8051 assembly language program to compute the average soil moisture for a day. (Sum may be assumed to be less than FFH). If the average value is less than moisture content 60, then write FFh in 80H location.

(3) Show the stack and stack pointer for each line of the following program.

MOV SP,#70H

MOV R5,#66H

MOV R2,#7FH

MOV R7,#5DH

PUSH 5

PUSH 2

PUSH 7

CLRA

MOV R2,A

MOV R7A

MOV R5,A

POP 7

POP 2

POP 5