Digital Electronics practice problem-2 (GATE-2014 EE)


Which of the following is an invalid state in an 8-4-2-1 Binary Coded Decimal Counter?

(a) 1 0 0 0
(b) 1 0 0 1
(c) 0 0 1 1
(d) 1 1 0 0


d)1100 .If it is converted in decimal you will get 12.that is invalid in BCD counter.


D) 1100
BCD counter means only we get the value till 9.


Answer is C-because Bcd number is valid total less than 8


Sorry total less than 9 not option a 8<9,b:9=9,c:3<9,d:12>9.only option C satisfy the condition (total <9)


@Jp123 im little bit confused because 8<9 also 3<9 so why the answer is option is C.
I think D part should be the correct option.


Hai good evening.Decimal number(1100)is equal to 12(in bcd).but in bcd we can represent up-to 9 in decimal(other than we can not represent. In case we present we follow another method). So those digital number can represent in bcd that digital number total in bcd should satisfy condition (<9).in the given question these condition satisfy the option A, C.(we can tick either A or c they given mark) and thank you Harsh for asking question.


hello @jp123 here they have asked invalid state in bcd counter so option d is correct naa


because here 8<9 , 9=9
3<9 and 12>9 so d is correct answer
Because it is invalid​:blush::blush:


Yes.option D is invalid state


option D is invalid state as the range of BCD is from 0 to 9.


Answer is D,because is decimal 12


Ans D . I.e 1100 is invalid state for BCD counter