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Convert SR F/F to D F/F.

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Convert SR F/F to D F/F.

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written 3.1 years ago by |

*SR flip-flop to D flip-flop:*

Qn | Qn+1 | R | S |
---|---|---|---|

0 | 0 | x | 0 |

0 | 1 | 0 | 1 |

1 | 0 | 1 | 0 |

1 | 1 | 0 | x |

*Excitation table for SR flip flop*

Qn | Qn+1 | D |
---|---|---|

0 | 0 | 0 |

0 | 1 | 0 |

1 | 0 | 1 |

1 | 1 | 0 |

*Excitation table for D flip flop*

- In the D flip flop excitation table, when D=0 and Q=0, the next state Q (t+1) is 0. For the next state to remain 0, the value of R and S should be X and 0 respectively. Here, X denotes don’t care value. The value of R in this condition, will not affect the state of the system. R=X and S=0.
- When D=0 and Q=1, the value of Next state Q (t+1) should be 0. (Refer to D flip-flop truth table). Here, there is a transition from 0 to 1 [Q=1 and Q (t+1) =0]. The RS input which corresponds to this transition is S=0 and R=1
**.** - When D=1 and Q=0, the value of next state Q (t+1) should be 1 (from D flip-flop truth table). Here, there is 0 to 1 transition. The value of R and S should be 0 and 1 respectively. R=0 and S=1.
- When D=1 and Q=1, the value of next state should be equal to 1 (from D flip-flop truth table). Here, there is a transition. The value of R and S corresponding to this transition is 0 and X respectively. X here represents don’t care condition. R=0 and S=X.

*K-map simplification:*

*Logic diagram:*

*T flip-flop to D flip-flop:*

- Both T flip-flop and D flip-flop have only 1 input each, T and D.
- T in the T-Flip flop stands for Toggle flip-flop, which means when the input is high, the output changes or ‘toggles’ its state.
- Thus the truth table and excitation table of T flip-flop are as shown:

T | Qn+1 |
---|---|

0 | Qn |

1 | Qn |

*Truth table of a T Flip-Flop*

Qn | Qn+1 | T |
---|---|---|

0 | 0 | 0 |

0 | 1 | 1 |

1 | 0 | 1 |

1 | 1 | 0 |

*Excitation table of a T Flip-Flop*

- D in the D-Flip flop stands for ‘Delay’ flip-flop, which means the output follows the input after a delay of one clock pulse. Output sets when input is high, and resets when input is low.
- Thus, its truth table and excitation table can be made as:

D | Qn+1 |
---|---|

0 | 0 (Reset) |

1 | (Set) |

*Truth table of a D Flip-Flop*

| Q | | | --- | --- |

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