mock interview questions of a linux and verilog

7/26/2019 Mock Interview Questions Of a linux and verilog

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1. How to find word which is occuring number of times with linux in just one command?Ans:With Grep Command:

grep -o 'needle' file | wc -l

With AWK command:awk -F'^needle | needle | needle$' '{c!"F-#%"&{print c'

2. What is grep !?Ans:oo find pattern matching word( )*e grep command + it *witch -, i* added then the fo)nd wordwill e neglected incl)ding that raw.

". How to find pattern in #$%?

Ans:*tring match f/ foo

&. what is diff between bloc'ing ( nonbloc'ing? explain with example.Ans:-0locking a**ignment* e,al)ate the 123 and )pdate the 423 witho)t interr)ption from an5other ,erilog *tatement-A nonlocking a**ignment e,al)ate* the 123 at the eginning of the time *tep and )pdate* the423 at the end of the time *tep.

mod)le lock6nonlock789reg a( ( c( d ( e( f 9 0locking a**ignment*initial egina ! ;#< #'#9 he *im)lator a**ign* # to a at time #< ! ;=< #'.\= eI8. hi* mean* that it take* onl5#.U= eI of energ5 to donate one of the *odi)m electron* to chlorine when the5 are far apart. Whenthe re*)ltant ion* are ro)ght clo*er together( their electric potential energ5 ecome* more and morenegati,e( reaching -#.U= eI at ao)t


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pol5*ilicon( i.e.( *ilicon formed from man5 *mall cr5*tal*. he middle la5er i* a ,er5 thin in*)-lating film of 3iH= called the gate oBide. he ottom la5er i* the doped *ilicon od5. he fig)re*how* a p-t5pe od5 in which the carrier* are hole*. he od5 i* gro)nded and a ,oltage i* appliedto the gate. he gate oBide i* a good in*)lator *o almo*t Lero c)rrent flow* from the gate to theod5.

62. 3xplain c/4s i!erterA5 :

o) can ea*il5 *ee that the CH3 circ)it f)nction* a* an in,erter 5 noting that when IJ" i* fi,e,olt*( IH i* Lero( and ,ice ,er*a. h)* when 5o) inp)t a high 5o) get a low and when 5o) inp)ta low 5o) get a high.

6". What is %atchup ?A5 :

CH3 *tr)ct)re i* a pair of para*itic ipolar tran*i*tor*. he collector of each 0M i* connected tothe a*e of the other tran*i*tor in a po*iti,e feedack *tr)ct)re.A phenomenon called latch)p can occ)r when:7#8 oth 0M'* cond)ct( creating a low re*i*tance path etween Idd and G"& and7=8 the prod)ct of the gain* of the two tran*i*tor* in the feedack loop( # B =( i* greater than one.he re*)lt of latch)p i* at the minim)m a circ)it malf)nction( and in the wor*t ca*e( the de*tr)ctionof the de,ice.4atch)p ma5 egin when Io)t drop* elow G"& d)e to a noi*e *pike or an improper circ)ithook)p 7Io)t i* the a*e of the lateral "N" O=8. Jf *)fficient c)rrent flow* thro)gh 1*) to t)rn onO= 7J 1*) P


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eno)gh( O# will al*o t)rn on( and a *elf-*)*taining low re*i*tance path etween the power rail* i*formed.Jf the gain* are *)ch that # B = P #( latch)p ma5 occ)r.Hnce latch)p ha* eg)n( the onl5 wa5 to *top it i* to red)ce the c)rrent elow a critical le,el()*)all5 5 remo,ing power from the circ)it.

Preventng lachup:

#8. 1ed)ce the gain prod)ct # B # mo,e n-well and n *o)rcedrain farther apart increa*e* width of the a*e of O= and red)ce*

gain eta= P al*o red)ce* circ)it den*it5 )ried n la5er in well red)ce* gain of O#

=8. 1ed)ce the well and *)*trate re*i*tance*( prod)cing lower ,oltage drop* higher *)*trate doping le,el red)ce* 1*)

red)ce 1well 5 making low re*i*tance contact to G"&

g)ard ring* aro)nd p- andor n-well( with fre)ent contact* to the ring*( red)ce* the para*itic

re*i*tance*.

6&. -/ seuence for 1011Ans:


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6). 3xplain : etup and Hold time

An*: 3et)p ime: he time re)ired for the inp)t data to e *tale efore the triggering clock edge.

3o( 3et-)p check e*tali*he* that the path i* fa*t eno)gh for the de*ired clock fre)enc5.

2old ime:

he time re)ired for the data to remain *tale after the triggering clock edge.

3o( hold check en*)re* that the path i* not too fa*t *o that data i* not pa**ed thro)gh.

2ow to remo,e

3et)p + 2old

,iolation*:

o *ol,e *et)p ,iolation

#. 05 optimiLing and re*tr)ct)ring the cominational logic etween the flop* of de*ign. Jn

ig de*ign*( we dont do thi* 5 o)r*el,e*( generall5 tool doe* thi* for )*. And what are the

wa5* that tool follow* for the *ameb We'll di*c)** that in neBt po*t.


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=. 05 )*ing `weak flop*X to offer le** *et)p dela5. 3ince( weak la)nch-flop ha,e etter

*lew at the clock pin and thi* make* CK-PO of la)nch flop fa*ter( *o that it help* in fiBing

*et)p ,iolation*.

>. 05 )*ing *ef)l- *kew*.

o *ol,e 2old Iiolation*

#. 05 adding dela5)ffer cell. 3ince the *imple )ffer offer* le** dela5( *o we )*e *pecial

&ela5 cell* who*e f)nctionalit5 remain* *ame( i.e. !A( )t with more dela5.

=. 05 pro,iding dela5 to the la)nch flop clock.

>. Where the hold time re)irement i* h)ge( we can )*e 4ock-)p 4atche* al*o.

6+. As8nchronous ,-- !eilog code

An* : mod)le dff6a*5nc6re*et 7data ( clk (re*et(89

inp)t data( clk( re*et 9

o)tp)t 9reg 9alwa5* D 7 po*edge clk or negedge re*et8if 7Yre*et8 egin ! #'8HptimiLation

6. How man8 times ,-# comes into the picture and when?

An* : &F will e done after *5nthe*i* and after man)fact)ring.

6. 9p of logic s8nthesis.

An*: V-----1e)ire* inp)t*:

7#8 14 file*.

7=8 35nop*5* Con*traint* file (&e*ign con*traint* file.

7>8 echnolog5 *pecific lirarie*.

V-----Jt* H)tp)t :

Gate le,el netli*t which i* technolog5 dependent.


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66. What is.sdc and .sdf files?An*: he 3&F file eBten*ion can e )*ed a* a *ched)le data file( a *o)rce definition file( a *tandarddata format( a *tandard dela5 format( and a *5*tem data format.

he 3&F file eBten*ion i* a data file with a fiBed length of A3CJJ( when it work* a* a *5*tem dataformat file. 0)t when it f)nction* a* the *tandard dela5 format( the 3&F file eBten*ion ecome* an

HIJ *tandard and it i* )*ed to repre*ent and interpret the different timing of data( which will e)*ed for the proce** of electronic de*igning.

3&F - 3tandard &ela5 Format*ed to con,e5 the timing information of a de*ign after implementation 7it can e generated at allof ao,e *tep*8. hi* i* what *a5* what* the dela5 at each cell( net( node. hi* i* eBported to do the*im)lation of de*ign and to find if the de*ign i* operating at the Fre)enc5 witho)t an5 *et)phold,iolation*.

&e*ign Compiler generate* 3&C file* 735nop*5* &e*ign Con*traint*8

Jt i* clear from the replie* here that man5 of 5o) ha,e not done a real chip de*ign. o) do need aQ*eedQ *dc file which define* clock* and inp)to)tp)t dela5* for the *5nthe*iLer. Jt *ho)ld al*o ha,efal*e path*( m)ltic5cle path*( and generated clock*. After *5nthe*i* 5o) generate a "%W *dc from&C( 5o) get man5 new path* generated( lot* of net*. o) r)n Nrimetime on thi* netli*t and read inthat *dc. After all the fal*e timing path* ha,e een anal5Led and con*traint* are )pdated( 5o) write anew *dc which i* gi,en to Nn1. Nrimetime i* r)n *e,eral time*: po*t-*5nth( after FloorNlanning +Gloal Nn1( after C3 + &etailed 1o)te( and after Nara*itic eBtraction.

3&C - 35nop*5* &e*ign Con*traint*hi* file i* )*ed for all implementation tool* *tarting from *5nthe*i*( timing anal5*i*(place+ro)te(dft(fpga..etc. hi* i* ,er5 important file to en*)re proper operation of 5o)r de*ign(fpga( *ilicon.

100. WhatMs the difference between the target librar8 to the lin' librar8 in 8nops8s ,$setup?An* :link6lirar5: i* the lirar5 5o) )*e component* from target6lirar5: i* the lirar5 5o) *5nthe*i*e to Jf 1A or N44 i* incl)ded it will e in link6lirar5 and not the target6lirar5.101. linux cmds:An* : 7#8 awk

7=8 grep

7>8find 7?8*ed 7U8*h)tdown

102. ,-# Z scanchain;scanreordering

What are scan chains: 3can chain* are the element* in *can-a*ed de*ign* that are )*ed to *hift-inand *hift-o)t te*t data. A *can chain i* formed 5 a n)mer of flop* connected ack to ack in achain with the o)tp)t of one flop connected to another. he inp)t of fir*t flop i* connected to theinp)t pin of the chip 7called *can-in8 from where *can data i* fed. he o)tp)t of the la*t flop i*connected to the o)tp)t pin of the chip 7called *can-o)t8 which i* )*ed to take the *hifted data o)t.

he fig)re elow *how* a *can chain.


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10". can $hain Beordering:*can chain reordering i* a proce** which i* done in the ph5*icalde*ign to optimi*e the conge*tion while doing placement. When we do *can 3titching ( we do notha,e( re*i*tor which are placed far from each other )t getting *titched in *ame *can chain. Al*othe5 ma5 not e ha,ing an5 ,alid path* etween them(f)nctionall5.hence ph5*ical de*ign tool (ha*to ro)te etween the*e two far awa5 FlipFlop )*t for *can p)rpo*e.0)t with *can reordering( theph5*ical de*ign toolreordering the re*i*tor* in the chain *ed on the placement of them to red)ce the

wire length.

10&.-rom how man8 wa8s we can 3xtract perticular string from file?

*ing lin)B command line awk

*ed

*ing perl *cripting 3plit 5o)r report from `:X and p)t it into arra5

now appl5 reg)lar eBpre**ion for *tring which 5o) want to find

print that element

C4 *cripting A* J *aid *plit 5o)r file with repeatation character and make li*t

Appl5 regB and find *tring

print

10). What happen if we swap nmos amd pmos in circuit?

fir*t if we *wap nmo* and pmo* than we will not get eBact U, at o)tp)t *ide.*econd it will work a* an in,erter

From thi* we al*o know ao)t wh5 pmo* pa** *trong # and nmo* pa** *trong


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10+. ,esign flow of design !ision 8nhesis tool?

10. #ell me in brief about $onstrains?


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part rai*ed like Fin *tr)ct)re in FinF% tran*i*tor*( *o the*e tran*i*tor* are called FinF%*. *)all5(thi* kind of protr)ding part* will allow power to pa** thro)gh all three part* at the *ame time. Al*o(it will allow m)ltiple tran*i*tor* to *hare a common gate and common contact* *o the )ltimatepower *)ppl5 con*)mption will *ignificantl5 e red)ced. Hk ( *o J will tr5 to p)t it in *imple word*.FinF% technolog5 will allow chip*et maker* to )ild )ltra-powerf)l proce**or*( which onl5 take alittle power when compared to traditional planar tran*i*tor*.

111. huzaifa_ab.*/-_kapasi--Detect a pattern like this.

An*. Sw_T_6a_._/__-_6Sw_T.

112.huzaifa.txt and abc.txt which contains word huzaifa.If we write erep -r huzaifa.txt thenwhat it returns!An*. ac.tBt:h)Laifa

11".#o print $ultiples of % till 1& usin shell scriptin

An*. "!Ui!#

while S$i -lt ##Tdoecho Q $n B $i ! eBpr $n _/ $iQi!eBpr $i #done

11'. Displa( hashes accordin to ke( )alues

An*.foreach m5 $name 7*ort ke5* ]planet*8 {printf Q]-[* ]*_nQ( $name( $planet*{$name9

11%. Different $ethods to find the lenth of arra(An*. Dlength ! $;arra5#.

print *calar7Darra5#8$length ! Darra5

11. +hat is sensiti)it( list!what if we specif( , for all the para$eters inside it!An*. Jt i* the no. of parameter* which are *pecified while triggering a lock.

Jf an5 of the parameter* *pecified in the *en*iti,it5 li*t change* then the lock get* eBec)tedagain.Jf we *pecif5 + then if all the parameter* change* then onl5 the lock get* triggered.

11. +h( we need to store the output )alues as re!what if the output is not dri)in an( load!

An*. 0eca)*e in the alwa5* lock it i* not contin)o)* a**ignment th)* )ntil the lock i* triggeredagain we need to *tore the o)tp)t ,al)e* th)* reg i* re)ired to e defined for e,er5 o)tp)tport.Jf o)tp)t i* not dri,ing an5 load then it will e floating(th)* in that ca*e al*o we need to *toreit a* reg.

11. xa$ple related to blockin and non-blockinAn*. Jnitiall5 a !>(!U(c![9

a!9! c9c ! a9

the o)tp)t will e a!U( c! U( ! [9


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110. +h( dela(s are not s(nthesizable!An*.Z 0eca)*e there i* no hardware to de*crie dela5.

12&. +h( we write ports in # and in desin file as opposite of each other!An*.#< 0eca)*e 0 i* the top le,el mod)le which i* dri,ing the & th)* the port* that are inp)t

for & are o)tp)t* of 0 act)all5 and the *ame goe* for inp)t port*.h)* we write port* a*oppo*ite of each other in 0 and &.

121.$os structure and characteristics of output )oltaeAns.

CMOS structure

Id vs d characteristics

122. +hat is threshold )oltae!

An*. Jt i* the minim)m ,oltage re)ired to e applied to the de,ice to t)rn it H".

12".+hat is the i$pact of chane in ate )oltae on the de)ice!

An*. Jf the gate ,oltage decrea*e* then the no. of electron* in ca*e of nmo* are le** attracted a* a

re*)lt weak channel i* formed(th)* c)rrent from drain to *o)rce will e le**.


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12'. +hat is s(nthesis!An*. Jt i* the proce** of con,erting 14 de*ign to Gate le,el netli*t *o that it can e f)rther done

for ph5*ical de*ign of the re)ired de*ign.

12%. +hat are the contents of .sdc files!

An*. Jt de*crie* the defa)lt ,al)e* for inp)t dela5(o)tp)t dela5(clock latenc5(maB tran*ition(*etting

inp)t and o)tp)t port*(m)ltic5cle path(etc.

12. 3rocess of s(nthesis!

An*. Fir*t the de*ign file i* read and then efore compile it map* acc. o Gtech li. And de*ignware li. And then con*traint* are gi,en and then afte compilation it i* mapped acc. o tech.4i. And then ,ario)* report* are generated and checked whether &1C are ,iolated or not.Jf,iolated then con*traint* are changed and then report* are again generated )ntil all &1C arefiBed.

12.+hat is dft wh( we need it and how it is done!

An*. Jt i* )*ed to te*t the man)fact)red hardware.

We need it eca)*e we don't ha,e an5 acce** to hardware if the fa)lt i* generated d)ringman)fact)ring or not.h)* to ha,e controlailit5 and o*er,ailit5 at the top le,el we need it.Jt i* done 5 ,ario)* method* *)ch a* 3can chain(ANG(0J3(MAG(etc.

12. Difference between $eal( and $oore $achineAns.

120. Difference between windows and linux

Ans. 4in)B i* open *o)rce while window* i* not.We ha,e acce** to *o)rce code in lin)B while in window* we don'tWe can modif5 acc. o o)r own in lin)B while in window* we don't.

1"&. +h( linux is )irus free!

Ans. Jn lin)B to in*tall an5thing we need to go to root direc. Which re)ire* pa**word th)* an5g)e*t7,ir)*8 will not ha,e an5 acce** to the *5*tem th)* it i* ,ir)* free while in window* toin*tall an5thing we need to r)n a* admini*trator which doe* not re)ire an5 pa**word th)* iti* not ,ir)* free.


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1"1. 4ultiplication #able of %.An*:"!Ui!#while S$i -lt ##Tdo

echo Q $n B $i ! eBpr $n _/ $iQi!eBpr $i #done

1"2. ls 5lrtAn*:l* for li*t commandl -li*tr- re,er*et- time

1"". 6a)iourite co$$and of linux.An*:cd l* pwd etc.

1"'. o$$and to check in which director( we are in )i editor

An*:pwd

1"%. 7ow to o in pre)ious director( usin co$$and

An*:

cd -

1". 6ind the word fro$ zip fileAn*:)*ing Lgrep command

1". 8(ntex rep co$$and.

An*:grep 'word' inp)tfile name

1". Difference in hash and arra(.

An*:Arra5* are ordered( integer-indeBed collection* of an5 oect. Arra5 indeBing *tart* at


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1"0. If I print % ti$es hash and fi)e ti$es arra( what will be the difference in the outputAn*:thre will e no change in o)tp)t.

1'&. 8ortin of a hash in alphabetic orde

An*:

foreach m5 $name 7*ort ke5* ]planet*8 {

printf Q]-[* ]*_nQ( $name( $planet*{$name9

thi* *5ntaB will gi,e *orted ,al)e*.

1'1. Difference in a and 9a

An*:a i* )*ed to define the ,ariale and $a will e )*ed to fetch the ,al)e which i* *tored in that ,ariale.

1'2. " wa(s to print how $an( )alues are there in an( arra(.

An*:

m5 Darr ! 7=89print *calar Darr9

m5 $arr3iLe ! Darr9print $arr3iLe9

m5 Dplanet* ! w7merc)r5 ,en)* earth mar* )piter89

m5 $*iLe ! $;planet* #9 print Q$*iLe_nQ9

1'". Difference of $eal( and $oore.

An*:

1''. +hat cho$p does.An*:chomp remo,e* the la*t new line character.


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1'%. +hat is as(nchronous and s(nchronous reset.An*:35nchrono)* 1e*etA *5nchrono)* re*et *ignal will onl5 affect or re*et the *tate of the flip-flop on the acti,e edge of theclock. he re*et *ignal i* applied a* i* an5 other inp)t to the *tate machine.

A*5nchrono)* 1e*et

An a*5nchrono)* re*et will affect or re*et the *tate of the flip-flop a*5nchrono)*l5 i.e. no matterwhat the clock *ignal i*. hi* i* con*idered a* high priorit5 *ignal and *5*tem re*et happen* a* *oona* the re*et a**ertion i* detected.

1'. 7ow c$os characteristics and when pinch off occure Id e:uation at pinchoff.An*:

Ninch of will take place when ,d* and more then ,d*at. And ,er5 *mall amo)nt of c)rrent will pa**.


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1'. +hat is bod( effect.

An*:

For *implicit5 ( it i* a**)med that the *o)rce and the )lk of the tran*i*tor are tied together ( )t inrealit5 it i* not.Jt i* one of the 3econd-Hrder effect* in anal5*i* of a mo*fet.

he ,oltage difference etween the *o)rce and )lk7*)*trate8 7I*8 affect* Ith of tran*i*tor.

And in order to *ee the od5 effect in tran*i*tor 5o) ha,e to add a c)rrent *o)rce in the drain of the*mall *ignal model of a mo*fet.it i* parallel with ro re*i*tor and gm/Iin c)rrent *o)rce. and it*,al)e i* gm/I*.

1'. Application of 8heban line in shell scriptinAn*:he ;E *5ntaB )*ed in *cript* to indicate an interpreter for eBec)tion )nder "J 4in)B operating*5*tem*.

1'0. xplain nand2 or nor2 c$os.

An*:

1%&. ;pti$ization techni:ues in loic 8(nthesis.

An*:Architect)ral optimiLation

arithmeticre*o)rce *haring

de*ign ware implementationgate le,el optimiLation

area optimiLationtime optimiLation

logic optimiLation

*tr)ct)ringflattening


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1%1. onstraints in loic s(nthesis.An*:&e*ign r)le con*traint*

maB tan*itionmaBmin capacitancefano)t

HptimiLation con*traint*maB areamaB timing

1%2. #(pes of leakae current in 4;8 explain all currents.An*:3)thre*hold cond)ction when the tran*i*tor* are off

)nnelling c)rrent thro)gh gate oBide

4eakage c)rrent thro)gh re,er*e-ia*ed diode*

1%". Initial block is s(nthesizable or not!An*:Jt i* not *5nthe*iLale.

mock interview questions of a linux and verilog

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