GATE 2000 Questions on Micro processor

One mark questions:

Question 1:

The number of hardware interrupts (which require an external signal to interrupt) to present in an 8085 microprocessor are

(a)   1
(b)   4
(c)   5
(d)   13

Answer: 5

Brief:
1. TRAP
2. RST 7.5
3. RST 6.5
4. RST 5.5
5. INTR

Explanation::https://docs.google.com/file/d/0B_-K2XS49Uc5SkgxSXFmcUU1R2M/edit?usp=sharing

Question 2:

In the 8085 microprocessor, the RST6 instruction transfers the program execution to the following location:

(a) 30H      (b) 24H     (c) 48H     (d) 60H

Answer: 30H

Explanation: Given in the above document Page no:13

Two mark questions:

Question 3:

The contents of Register (B) and Accumulator (A) of 8085 microprocessor are 49H and 3AH respectively. The contents of A and the status of carry flag (CY) and sign flag (S) after executing SUB B instructions are

(a) A=F1, CY=1, S=1
(b) A=0F, CY=1, S=1
(c) A=F0, CY=0, S=0
(d) A=1F, CY=1, S=1

Answer: (a) A=F1, CY=1, S=1

Explanation:

(A) => 3AH => 00111010
(B) => 49H => 01001001
                         ------------------
                          11110001
(A) => F1H
(CY) => 1
(S) => 1

The carry flag is set since the first operand is less than the second operand.
Since the result produces the negative result sign flag is set

Explanation Reference click here