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A state transition diagram has to be drawn for the following scenario. (Later it has to be implemented using D flipflops)

Scenario:-

A sequential machine to resolve a 4-bit security code. The code is "1010" and it is sent to the resolving circuitry as a sequence of bits. The output of the detector should be raised to 1 if and only if the correct code is detected.

It says the code is sent as a sequence of bits and I tried to come up with the state transition diagram as below.

enter image description here

Is it correct? Or is there something missing?

asked Aug 18, 2015 at 13:45
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  • \$\begingroup\$ It's missing an accept indicator and the fact that the code must be 4 bits long. \$\endgroup\$ Commented Aug 18, 2015 at 13:46
  • \$\begingroup\$ @IgnacioVazquez-Abrams How to check for the length of the code? \$\endgroup\$ Commented Aug 18, 2015 at 13:59

1 Answer 1

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For an input 1 the output will be 1. As for any code ending with 1. So it is incorrect. As a general rule - for detection of a sequence with length N you need N states for Moore machine or N-1 for Mealy machine (your case).

answered Aug 18, 2015 at 17:05
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