Embedded systems interview questions and answers for freshers

What is lst file?

- This file is also called as list file.
- It lists the opcodes ,addresses and errors detected by the assembler.
- List file is produced only when indicated by the user.
- It can be accessed by an editor and displayedon monitor screen or printed.
- Progammer uses this file to find the syntax errors and later fix them.

How is a program executed’ bit by bit’ or’ byte by byte’?

1   0000ORG 0H
2   00007D25MOV R5,#25H
3   00027F34MOV R7,#34H
4   00042DADD A, R5
5   0005END

- A program is always executed byte by byte.
- Firstly,1st opcode 7D is fetched from location 0000 and then the value 25 is fetched from 0001 .
- 25 is then placed in the register R5 and program counter is incremented to point 0002.
- On execution of opcode 7F, value 34 is copied to register R7.
- Then addition of contents of R5 and accumulater takes place.
- Here all the opcodes are 8 bit forming a byte.

Explain DB.

- DB is called as define byte used as a directive in the assembler.
- It is used to define the 8 bit data in binary ,hexadecimal or decimal formats.
- It is the only directive that can be used to define ASCII strings larger than two characters.
- DB is also used to allocate memory in byte sized chunks.
- The assembler always converts the numbers lnto hexadecimal.

What is EQU?

- EQU is the equate assmbler directive used to define a constant without occupying a memory location.
- It associates a constant value with data label .
- Whenever the label appears in the program ,constant value is subsituted for label.
- Advantage: The constant value occuring at various positions in a program can be changed at once using this directive.
- Syntax: label EQU constant value

How are labels named in assembly language?

- Label name should be unique and must contain alphabetic letters in both uppercase and lowercase.
- 1st letter should always be an alphabetic letter.
- It can also use digits and special characters ?,.,@,_,$.
- Label should not be one of the reserved words in assembly language.
- These labels make the program much easier to read and maintain.

Are all the bits of flag register used in 8051?

- The flag register also called as the program status word uses only 6 bits.
- The two unused bits are user defineable flags.
- Carry, auxillary carry, parity and overflow flags are the conditional flags used in it.
- PSW.1 is a user definable bit and PSW.5 can be used as general purpose bit.
- Rest all flags indicate some or the other condition of an arithmetic operation.

Which bit of the flag register is set when output overflows to the sign bit?

- The 2nd bit of the flag register is set when output flows to the sign bit.
- This flag is also called as the overflow flag.
- Here the output of the signed number operation is too large to be accomodated in 7 bits.
- For signed numbers the MSB is used to indicate the whether the number is positive or negative.
- It is only used to detect errors in signed number operations.

Which register bank is used if we use the following instructions.
SETB PSW.3       A
SETB PSW.4       B

- Statement A sets 3rd bit of flag register.
- Statement B sets 4th bit of flag register.
- Therefore register bank 3 is initiated .
- It uses memory location 18H to 1FH.
- The register bank is also called as R3.

Issues related to stack and bank 1.

- Bank 1 uses the same RAM space as the stack.
- Stack pointer is incremented or decremented according to the push or pop instruction.
- If the stack pointer is decremented it uses locations 7,6,5… which belongs to register bank 0.
- If a given program uses R1 then stack is provided new memory location.
- The push instruction may also take stack to location 0 i.e.it will run out of space.

Explain JNC.

- It is a command used to jump if no carry occurs after an arithematic operation.
- It is called as jump if no carry( conditional jump instruction).
- Here the carry flag bit in PSW register is used to make decision.
- The processor looks at the carry flag to see if it is raised or not.
- If carry flag is 0 ,CPU fetches instructions from the address of the label.
1 2

VLSI interview questions and answers, VLSI FAQs
VLSI interview questions - Stuck-at-faults, ATPG, Explain cross-talk. How can it be divided?, Explain charge sharing between bus and memory element,How would you make a XOP gate using NAND gates?.....
Data Structures Arrays - Answers to Arrays related interview questions
Data Structures Arrays - In this series, we have covered all about Arrays and answered the questions that might be asked during an interview.
Linked list interview questions and answers - freshers, experienced
Data Structures Linked list - In this series, we have covered all about Linked list and answered the questions that might be asked during an interview.
Post your comment
Discussion Board
embeded system
any one pls tel how to get embeded job for freshers.
sivanathan 09-2-2015
It's really very useful, Thank you.
please forward the similar questions to my mail id
Embedded system
sir really its very usefull for me . thaks sir
Pavan 07-8-2015
Embedded system
sir really its very usefull for me . thaks sir
Pavan 07-8-2015
plz Tell me some Embedded Domain companies list
Those Interview questions are awsome and very usefull, Can any body give me some of the embedded companies list for freshers
suneel 07-5-2015
electronics engineer
i am interested in embedded system, so please share some embedded companies with me on my email i.d.
anurag dixit 02-18-2015
Hi my name is Yoghanandh I finished DEEE , and aslo having experince in pcb assembling
and having the knowledge in embedded system, good knowledge in c,c++, Emb c,8051,PIC,Emb networking.
YOGHANANDH 07-28-2014
msc electronics
it is very good for freshers .it will give the knowledge about embeded system in advanced method
sudheer 07-6-2014
Embeeded system
I am diploma electronic communication completed interested in embeeded system job vacency please kindly us me
Vinothkumar 06-25-2014
very useful for freshers please up load more question and answers
t.gowtham 01-9-2014
please upload more que and ans
vivek kumar 12-27-2013
its gud & helpful.upload more question & ans
madhu 10-23-2013
Its useful thanx
Karthick mp 04-16-2013
fresher embedded engineer
very useful for me
murali 12-24-2012