The previous years question paper for the Telecom Technical Assistant recruitment examination conducted by Bharat Sanchar Nigam Limited is as given below:

BSNL TTA Paper
Microprocessors Specialization:
90 Marks
Basic Processing Unit


1. Specify the sequence of operation involved when an instruction is executed.
a)Instruction Fetch
b)Instruction Decode
c)Operand Fetch
d)Execute
e) Write Back

2. Define parallel processing.
Parallel processing is a term used to denote a large class of techniques that are used to
provide simultaneous data-processing tasks for the purpose of increasing the computational speed of a computer system. Instead of processing each instruction sequentially as in a conventional computer, a parallel processing system is able to perform concurrent data processing to achieve faster execution time.

3. Define sequential circuits.
A sequential circuit is an interconnection of flip-flops and gates. The gates by themselves constitute a combinational circuit, but when included with the flip flops, the overall circuit is classified as a sequential circuit.

4. Define interface.
The word interface refers to the boundary between two circuits or devices

5. Define processor clock.
Processor clock: Processor circuits are controlled by a timing signal called processor
clock, the clock defines regular time interval called clock cycle.

6. Define latency.
The term memory latency is used to refer to the amount of time it takes to transfer a
word of data to or from the memory. The term latency is used to denote the time it takes to transfer the first word of data. This time is usually substantially longer than the time needed to transfer each subsequent word of a block.

7. Define bandwidth.
Bandwidth is a product of the rate at which the data are transferred (and accessed) and
the width of the data bus.

8. Define hit rate.
A successful access to data in a cache is called a hit. Number of hits stated as a fraction of all attempted accesses is called the hit rate.

9. Define miss rate.
A miss rate is the number of misses stated as a fraction of attempted accesses. Extra time needed
to bring the desired information into the cache is called the miss penalty.

10. Define Clock Rate:
Clock rate, R=1/p cycles/sec(hz)
Where p is length of one clock cycle

11. What is micro programming and micro programmed control unit?
Microprogramming is a method of control unit design in which the control unit selection and sequencing information are stored in ROM and RAM’s called control store or control memory. Micro programmed control unit is a general approach used for implementation of control unit. Here control signals are generated by a program similar to machine language programs.

12. What is meant by hardwired control?
It is the one that contains control units that use fixed logic circuits to interpret instructions and generate control signals from them. Here,the fixed logic circuit block includes combinational circuit that generates the required control outputs for decoding and encoding functions.

13. What is Register Renaming?
If a temporary register assumes the role of the permanent register whose data it is holding and is given the same name is called as the Register Renaming.

14. What is the function of commitment unit?
When out-of-order execution is allowed, a s pecial control unit called as “commitment
unit” is used to guarantee in-order commitment. It uses a queue called the “reorder buffer” to determine which instruction should be committed next. This is the function of commitment unit.

15. Define the term Clock Rate.
They are two possibilities for increasing the clock rate, R. First, improving the IC
technology makes logic circuits faster, which reduces the time needed to complete a basic step.
This allows the clock period P to be reduce and the clock rate R to be increased Second, reducing the amount of processing done is one basic step makes it possible to reduce the clock period P.

16. What do you mean by out-of order execution? Is it Desirable?
In a pipelined processor with several instructions is process concurrently it is Possible
for instruction to finish out of sequence, one instruction finishes before Another which is issued earlier, as far as main computation is concerned no Hazards will happen but if an interrupts occurs it creates the problem.
17. Define Overflow
Overflow -In the single precision, if the number requires a exponent greater then +127
or in a double precision, if the number requires an exponent form the overflow occurs.
18. Define Underflow
Underflow-In a single precision ,if the number requires an exponent less than -26 or in a double precision, if the number requires an exponent less than -1022 to represent its normalized form the underflow occurs.
19. What are Condition Codes (CC)? Explain the use of them.
Condition Codes are the list of possible conditions that can be tested during conditional instructions. CC is used to test the condition (<, =,>). Based on this result, Jump instructions move to specified loop. CC flags represent the value of processor that keeps the information about the results of various operations for use by
conditional branches.
20. What is straight –line sequencing?
Process of fetching and executing an instruction; one at a time in order of increasing
address with the help of information in program counter