Assume that the memory is byte addressable and the word

Home » Computer Organization and Architecture » Computer organization and architecture miscellaneous » Question

Direction: Consider the following program segments. Here R₁, R₂ and R₃ are purpose registers.

Instruction	Operation	Instruction size (number of words)
MOV R₁, 3000	R₁ ← M [3000]	2
LOOP MOV R₂ , R₃	R₂ ← M [R₃]	1
ADD R₂,	R₂ ← R₁ + R₂	1
MOV R₃ , R₂	M[R₃] ← R₂	1
INC R₃	R₃ ← R₃ + 1	1
DEC R₁	R₁ ← R₁ – 1	1
BNZ LOOP	Branch on not zero	2
HALT	Stop	1

Assume that the content of memory location 3000 is 10 and the content of the register R₃ is 2000. The content of each of the memory locations from 2000 to 2010 is 100. The program is loaded from the memory location 1000. All the numbers are in decimal.

Assume that the memory is byte addressable and the word size is 32 bit. If an interrupt occurs during the execution of the instruction INC R₃, what return address will be pushed on to the stack?

1. 1005
2. 1020
3. 1024
4. 1040

Correct Option: C

An interrupt is checked for after the execution of the current instruction and the contents of PC (address of next instruction to be executed) is pushed on to stack.

Here, address of INC, R₃ = 1000 + (2 + 1 + 1 + 1) *		32		= 1020
		8

and next instruction address = 1020 + 4 = 1024 , which is pushed on to stack.