# Control Unit - Q4

+1 vote

A microprogram control unit is required to generate a total of $10$ control signals. Assume that during any micro instruction, at most $5$ control signals are active. Minimum number of bits required in the control word to generate the required control signals will be:

$(A)10$

$(B)9$

$(C)8$

$(D)7$

reshown Jun 9

+1 vote

total 10 control signal at most 5 active so

$total = _{0}^{10}\textrm{C}+_{1}^{10}\textrm{C}+_{2}^{10}\textrm{C}+_{3}^{10}\textrm{C}+_{4}^{10}\textrm{C}+_{5}^{10}\textrm{C} = 638$

$\lceil \log_2 (638)\rceil = \lceil 9.317 \rceil= 10$

So the option is A

answered Jun 9 by (4,120 points)
selected Jun 9
https://gateoverflow.in/2754/gate1996-2-25
Just See this question. If we try in this way we are not getting the correct answer.
actually for that 9 bits is the correct answer although there is no appropriate option so there assumed 5X32 and 5X32 decoder assumed in that way 10 bits
but in this question, I am getting option
Yes you might be right. But what is wrong with that approach( only disadvantage is  that we are not getting the answer). But question should be made in such a way that with any approach we should be getting the same answer.

With your approach they have to assume 9 bits answer as 10 bits but they all are getting exact answer without assuming anything with that approach.
It's same like that if we ask you to for 513 how may minimum bit required to represent in binary than answer is 10 but if option given

11
12
8
7
Than every one select 11
Because in given option best one is 11 but it is not minimum best is 10

Same here minimum is 10 because option otherwise minimum is 9 with the help of other concept.which one explain by Rishi Yadav.
This is an ideal approach you should follow if that option is not present go for the option which is near

@getgatebook

This question might be wrong because the answer to this question is not given in the options.

$\\ Total\ control\ signals=10\\ Number \ of\ bits=\log _{2}10=4\\ We\ assumed\ vertical\ microprogramming\ as\ minimum\ number\ of\ bits\ is\ asked\\ Atmost\ 5\ control\ signals\ active \\ \therefore Minimum\ number\ of\ bits\ required\ in\ the\ control\ word=5*4=20\ bits$

answered Jun 9 by (8,720 points)