analog design interview questions

[mdeepamenon]

job interview questions

here are some of the job interview questions.
:?:implement an ex-nor gate using ex-or gates only
:?:implement a NAND-gate using a single module of 2:1 mux only. dont use any combi. modules.
l:?t of questions on hold and settling time like: what happends to the output of a D FF if the data changes a)with in the settling time. b) within the hold time.
:?:what are the advantages of mealy and moore machines.

if you know the answers, please do post to this forum.

 

[gharuda]

Re: job interview questions

1, u can construct xnor with two xor gates.

apply two inputs to first xor gate and then give the output of first xor gate , to second xor gate and other input to Vdd.


2. Tie one of inputs of mux to logic 1 and other input to say BBAR and select line as A .

A B O
00 1
01 1
10 1
11 0

whenever select(A) signal is low .output will bw logic 1

when Slect (A) is high output will be BBAR.

 

[elecs_gene]

Re: job interview questions

hi,
i agree with the answers...if in the second case, u think Bbar can't be given as such, u can use a mux to invert b..for that, give ' 1'(VDD) and '0'(GND) as the input to 0 & 1 pin of the MUX...now give b as the selection line..now when b is '1', then '0' is sent out otherwise '1'........

if set up time and hold time were not met, then the output would be in -determinate state.....

regards,
elecs_gene

 

[foster_cn]

Re: job interview questions

what kinda of job position require the above questions?

 

[mdeepamenon]

Re: job interview questions

well, that were the questions asked for a job in the hardware lab of an MNC .

 

[kil]

Re: job interview questions

mealy machine is used where we need fast circuit design and where little glith probelms doesnt matter becoz we do not register the output of mealy data and it can some times called as asyn type state machine as it doesnt care about the clock edge where it cares about the present input and present state change.

where as moore machine the output is always registered so atleast one clock cycle data output delay will be there. where timing critical applications are there we go for moore based state machine design

if i am wrong plz correct me......................

kil

 

[mdeepamenon]

Re: job interview questions

then, what all advantages does the moore machine have? are you saying that big systems should have moore archi?

 

[tigerajs]

Re: job interview questions

you can do it by thinking

 

[sakthi_tallika]

Re: job interview questions

It depends on your requirement. for ex. if you want to detect a pattern and generate output while detecting the last bit of the particular pattern(no delay), mealy FSM will be more useful.

 

[foster_cn]

job interview questions

does any one konw what is the logic expression of a MUX?

 

[Ave_Rapina]

Re: job interview questions

A = 0 --> Out = Input0
A = 1 --> Out = Input1


Out = Input0 & /A + Input1 & A