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GATE 2014 EE (EE2) – Question 31

Analog and Digital Electronics · VCOs and timers, combinatorial and sequential logic circuits, multiplexers, demultiplexers · 1 mark · Multiple choice

Which is invalid in an 8-4-2-1 BCD counter?

  1. 1000
  2. 1001
  3. 0011
  4. 1100

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Show answer and explanation

Correct answer: (D) 1100

Explanation

8421BCD represents decimal digits0through9using binary0000through1001. Codes1010through1111are unused. The listed1100represents binary12and is therefore **invalid,D**;1000,1001and0011are valid encodings of8,9and3.