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Synchronous Sequential Circuits
        Class Revision Question
A synchronous sequential circuit is shown below which is
  comprised of three J-K flip-flops. (Let the flip-flops be
  numbered 1, 2 and 3 from the left hand side).




                 1            2                   3
The J-K Transition Table is:
             Synchronous Sequential Circuits
                Class Revision Question
    Assuming that the outputs Q1, Q2 and Q3 of the flip-flops
      are all initially in the '0' state, demonstrate the sequence
      that the circuit will clock through over the next 6 clock
      cycles by obtaining logic descriptions for each of the J-K
      inputs, and deriving each 'next-state' output from each
      'present-state' output using the J-K flip-flop transition table.
         (Ignore the set and clr of each flip-flop).



                                      J                K   Q(n+1)
                                      0                0    Qn      No Change
                                      0                1      0     Clear
                                      1                0      1     Set
                                      1                1     Qn     Toggles
The J-K Transition Table is:
             Synchronous Sequential Circuits
               Identifying Initial Conditions




 Looking at Flip Flop 1:- J1 = Q2
                               Similarly at Flip Flop 2:- J2 = Q3
   And also:- K1 = Q2
                                  And also:- K2 = Q3
The J-K Transition Table is:
             Synchronous Sequential Circuits
               Identifying Initial Conditions




 Looking at Flip Flop 3:- J1 = 1

             And also:- K3 = Q1.Q2 = (Q1 AND’ed with Q2)
The J-K Transition Table is:
             Synchronous Sequential Circuits
               Identifying Initial Conditions




                 Now let’s tabulate the synchronous conditions
                J1         K1    Q1    J2     K2    Q2   J3     K3      Q3
               (Q2)       (Q2)        (Q3)   (Q3)        1    (Q1.Q2)
The J-K Transition Table is:
             Synchronous Sequential Circuits
               Identifying Initial Conditions




                               And add the initial conditions
             J1          K1    Q1    J2     K2    Q2   J3     K3      Q3
            (Q2)        (Q2)        (Q3)   (Q3)         1   (Q1.Q2)
               Initial          0                 0                   0
              Condition
The J-K Transition Table is:
             Synchronous Sequential Circuits
              Starting to populate the table
    As Q2 = 0, J1 and K1 = 0.
    As Q3 = 0, J2 and K2 = 0.
    As Q1 = 0 & Q2 =0; Q1.Q2 = 0 so K3 = 0.
    (J3 is ALWAYS 1)




            J1           K1    Q1    J2     K2    Q2   J3     K3      Q3
           (Q2)         (Q2)        (Q3)   (Q3)         1   (Q1.Q2)
           Initial Condition   0                  0                   0


             0           0           0      0           1      0
The J-K Transition Table is:
             Synchronous Sequential Circuits
                  Populating the table
    J-K flip-flop transition table                         J           K      Q(n+1)
    (changes on the CLOCK pulse)
                                                           0           0       Qn
    J1 and K1 = 0:- Q1 (stays same) = 0.
                                                           0           1         0
    J2 and K2 = 0:- Q2 (stays same) = 0.                   1           0         1
    J3 = 1 & K3 = 0:- Q3 = 1.                              1           1           Qn



            J1          K1         Q1    J2     K2    Q2       J3     K3      Q3
           (Q2)        (Q2)             (Q3)   (Q3)            1    (Q1.Q2)
          Initial Condition        0                  0                       0

             0            0              0      0              1      0

                 Clock 1           0                  0                       1
The J-K Transition Table is:
              Synchronous Sequential Circuits
                   Populating the table
    As Q2 = 0, J1 and K1 = 0.                          J          K     Q(n+1)
    As Q3 = 1, J2 and K2 = 1.                          0          0      Qn
    As Q1.Q2 = 0 so K3 = 0.                            0          1        0
    (J3 is ALWAYS 1)                                   1          0        1
                                                       1          1          Qn

         J1          K1        Q1    J2     K2    Q2       J3     K3    Q3
        (Q2)        (Q2)            (Q3)   (Q3)            1    (Q1.Q
                                                                  2)
      Initial Condition        0                  0                     0

          0           0              0      0              1     0

            Clock 1            0                  0                     1

          0           0              1     1               1      0
The J-K Transition Table is:
             Synchronous Sequential Circuits
                  Populating the table
    J-K flip-flop transition table                            J                  K        Q(n+1)
    (changes on the CLOCK pulse)
                                                              0                  0         Qn
    J1 and K1 = 0:- Q1 (stays same) = 0.
                                                              0                  1           0
    J2 and K2 = 1:- Q2 (Toggles) = 1.                         1                  0           1
    J3 = 1 & K3 = 0:- Q3 (Set) = 1.                           1                  1          Qn

                       J1       K1    Q1    J2     K2    Q2       J3     K3          Q3
                      (Q2)     (Q2)        (Q3)   (Q3)            1    (Q1.Q2)
                         Initial      0                  0                           0
                        Condition
                        0       0           0      0              1      0

                         Clock 1      0                  0                           1

                        0       0           1      1              1      0

                         Clock 2      0                  1                           1
The J-K Transition Table is:
             Synchronous Sequential Circuits
                  Populating the table
    As Q2 = 1, J1 and K1 = 1.                                 J                K       Q(n+1)
    As Q3 = 1, J2 and K2 = 1.                                 0                0        Qn
    As Q1.Q2 = 0 so K3 = 0.                                   0                1          0
    (J3 is ALWAYS 1)                                          1                0          1
                                                              1                1         Qn
                       J1       K1    Q1    J2     K2    Q2       J3     K3    Q3
                      (Q2)     (Q2)        (Q3)   (Q3)            1    (Q1.Q
                                                                         2)
                         Initial      0                  0                         0
                        Condition
                        0       0           0      0              1     0

                         Clock 1      0                  0                         1

                        0       0           1      1              1     0

                         Clock 2      0                  1                         1

                        1       1           1     1               1     0
The J-K Transition Table is:
             Synchronous Sequential Circuits
                  Populating the table
    J-K flip-flop transition table                            J                  K        Q(n+1)
    (changes on the CLOCK pulse)                              0                  0         Qn
    J1 and K1 = 1:- Q1 (Toggles) = 1.                         0                  1           0
    J2 and K2 = 1:- Q2 (Toggles) = 0.                         1                  0           1
    J3 = 1 & K3 = 0:- Q3 (Set) = 1.                           1                  1          Qn
                       J1       K1    Q1    J2     K2    Q2       J3     K3          Q3
                      (Q2)     (Q2)        (Q3)   (Q3)            1    (Q1.Q2)
                         Initial      0                  0                           0
                        Condition
                        0       0           0      0              1      0

                         Clock 1      0                  0                           1

                        0       0           1      1              1      0

                         Clock 2      0                  1                           1

                        1       1           1      1              1      0

                         Clock 3      1                  0                           1
The J-K Transition Table is:
             Synchronous Sequential Circuits
                  Populating the table
                                                              J                  K        Q(n+1)
    As Q2 = 0, J1 and K1 = 0.
                                                              0                  0         Qn
    As Q3 = 1, J2 and K2 = 1.
                                                              0                  1           0
    As Q1.Q2 = 0 so K3 = 0.                                   1                  0           1
    (J3 is ALWAYS 1)
                                                              1                  1          Qn
                       J1       K1    Q1    J2     K2    Q2       J3     K3          Q3
                      (Q2)     (Q2)        (Q3)   (Q3)            1    (Q1.Q2)
                         Initial      0                  0                           0
                        Condition
                        0       0           0      0              1      0

                         Clock 1      0                  0                           1

                        0       0           1      1              1      0

                         Clock 2      0                  1                           1

                        1       1           1      1              1      0

                         Clock 3      1                  0                           1

                        0       0           1      1              1     0
The J-K Transition Table is:
                              Can you complete
                             Populating the table?
                       J1       K1    Q1    J2     K2    Q2   J3     K3      Q3
                      (Q2)     (Q2)        (Q3)   (Q3)        1    (Q1.Q2)
                         Initial      0                  0                   0
                        Condition
                        0       0           0      0          1      0

                         Clock 1      0                  0                   1

                        0       0           1      1          1      0

                         Clock 2      0                  1                   1

                        1       1           1      1          1      0

                         Clock 3      1                  0                   1

                        0       0           1      1          1      0

                         Clock 4



                         Clock 5



                         Clock 6

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Synchronous Logic Circuit Revision Q

  • 1. Synchronous Sequential Circuits Class Revision Question A synchronous sequential circuit is shown below which is comprised of three J-K flip-flops. (Let the flip-flops be numbered 1, 2 and 3 from the left hand side). 1 2 3
  • 2. The J-K Transition Table is: Synchronous Sequential Circuits Class Revision Question Assuming that the outputs Q1, Q2 and Q3 of the flip-flops are all initially in the '0' state, demonstrate the sequence that the circuit will clock through over the next 6 clock cycles by obtaining logic descriptions for each of the J-K inputs, and deriving each 'next-state' output from each 'present-state' output using the J-K flip-flop transition table. (Ignore the set and clr of each flip-flop). J K Q(n+1) 0 0 Qn No Change 0 1 0 Clear 1 0 1 Set 1 1 Qn Toggles
  • 3. The J-K Transition Table is: Synchronous Sequential Circuits Identifying Initial Conditions Looking at Flip Flop 1:- J1 = Q2 Similarly at Flip Flop 2:- J2 = Q3 And also:- K1 = Q2 And also:- K2 = Q3
  • 4. The J-K Transition Table is: Synchronous Sequential Circuits Identifying Initial Conditions Looking at Flip Flop 3:- J1 = 1 And also:- K3 = Q1.Q2 = (Q1 AND’ed with Q2)
  • 5. The J-K Transition Table is: Synchronous Sequential Circuits Identifying Initial Conditions Now let’s tabulate the synchronous conditions J1 K1 Q1 J2 K2 Q2 J3 K3 Q3 (Q2) (Q2) (Q3) (Q3) 1 (Q1.Q2)
  • 6. The J-K Transition Table is: Synchronous Sequential Circuits Identifying Initial Conditions And add the initial conditions J1 K1 Q1 J2 K2 Q2 J3 K3 Q3 (Q2) (Q2) (Q3) (Q3) 1 (Q1.Q2) Initial 0 0 0 Condition
  • 7. The J-K Transition Table is: Synchronous Sequential Circuits Starting to populate the table As Q2 = 0, J1 and K1 = 0. As Q3 = 0, J2 and K2 = 0. As Q1 = 0 & Q2 =0; Q1.Q2 = 0 so K3 = 0. (J3 is ALWAYS 1) J1 K1 Q1 J2 K2 Q2 J3 K3 Q3 (Q2) (Q2) (Q3) (Q3) 1 (Q1.Q2) Initial Condition 0 0 0 0 0 0 0 1 0
  • 8. The J-K Transition Table is: Synchronous Sequential Circuits Populating the table J-K flip-flop transition table J K Q(n+1) (changes on the CLOCK pulse) 0 0 Qn J1 and K1 = 0:- Q1 (stays same) = 0. 0 1 0 J2 and K2 = 0:- Q2 (stays same) = 0. 1 0 1 J3 = 1 & K3 = 0:- Q3 = 1. 1 1 Qn J1 K1 Q1 J2 K2 Q2 J3 K3 Q3 (Q2) (Q2) (Q3) (Q3) 1 (Q1.Q2) Initial Condition 0 0 0 0 0 0 0 1 0 Clock 1 0 0 1
  • 9. The J-K Transition Table is: Synchronous Sequential Circuits Populating the table As Q2 = 0, J1 and K1 = 0. J K Q(n+1) As Q3 = 1, J2 and K2 = 1. 0 0 Qn As Q1.Q2 = 0 so K3 = 0. 0 1 0 (J3 is ALWAYS 1) 1 0 1 1 1 Qn J1 K1 Q1 J2 K2 Q2 J3 K3 Q3 (Q2) (Q2) (Q3) (Q3) 1 (Q1.Q 2) Initial Condition 0 0 0 0 0 0 0 1 0 Clock 1 0 0 1 0 0 1 1 1 0
  • 10. The J-K Transition Table is: Synchronous Sequential Circuits Populating the table J-K flip-flop transition table J K Q(n+1) (changes on the CLOCK pulse) 0 0 Qn J1 and K1 = 0:- Q1 (stays same) = 0. 0 1 0 J2 and K2 = 1:- Q2 (Toggles) = 1. 1 0 1 J3 = 1 & K3 = 0:- Q3 (Set) = 1. 1 1 Qn J1 K1 Q1 J2 K2 Q2 J3 K3 Q3 (Q2) (Q2) (Q3) (Q3) 1 (Q1.Q2) Initial 0 0 0 Condition 0 0 0 0 1 0 Clock 1 0 0 1 0 0 1 1 1 0 Clock 2 0 1 1
  • 11. The J-K Transition Table is: Synchronous Sequential Circuits Populating the table As Q2 = 1, J1 and K1 = 1. J K Q(n+1) As Q3 = 1, J2 and K2 = 1. 0 0 Qn As Q1.Q2 = 0 so K3 = 0. 0 1 0 (J3 is ALWAYS 1) 1 0 1 1 1 Qn J1 K1 Q1 J2 K2 Q2 J3 K3 Q3 (Q2) (Q2) (Q3) (Q3) 1 (Q1.Q 2) Initial 0 0 0 Condition 0 0 0 0 1 0 Clock 1 0 0 1 0 0 1 1 1 0 Clock 2 0 1 1 1 1 1 1 1 0
  • 12. The J-K Transition Table is: Synchronous Sequential Circuits Populating the table J-K flip-flop transition table J K Q(n+1) (changes on the CLOCK pulse) 0 0 Qn J1 and K1 = 1:- Q1 (Toggles) = 1. 0 1 0 J2 and K2 = 1:- Q2 (Toggles) = 0. 1 0 1 J3 = 1 & K3 = 0:- Q3 (Set) = 1. 1 1 Qn J1 K1 Q1 J2 K2 Q2 J3 K3 Q3 (Q2) (Q2) (Q3) (Q3) 1 (Q1.Q2) Initial 0 0 0 Condition 0 0 0 0 1 0 Clock 1 0 0 1 0 0 1 1 1 0 Clock 2 0 1 1 1 1 1 1 1 0 Clock 3 1 0 1
  • 13. The J-K Transition Table is: Synchronous Sequential Circuits Populating the table J K Q(n+1) As Q2 = 0, J1 and K1 = 0. 0 0 Qn As Q3 = 1, J2 and K2 = 1. 0 1 0 As Q1.Q2 = 0 so K3 = 0. 1 0 1 (J3 is ALWAYS 1) 1 1 Qn J1 K1 Q1 J2 K2 Q2 J3 K3 Q3 (Q2) (Q2) (Q3) (Q3) 1 (Q1.Q2) Initial 0 0 0 Condition 0 0 0 0 1 0 Clock 1 0 0 1 0 0 1 1 1 0 Clock 2 0 1 1 1 1 1 1 1 0 Clock 3 1 0 1 0 0 1 1 1 0
  • 14. The J-K Transition Table is: Can you complete Populating the table? J1 K1 Q1 J2 K2 Q2 J3 K3 Q3 (Q2) (Q2) (Q3) (Q3) 1 (Q1.Q2) Initial 0 0 0 Condition 0 0 0 0 1 0 Clock 1 0 0 1 0 0 1 1 1 0 Clock 2 0 1 1 1 1 1 1 1 0 Clock 3 1 0 1 0 0 1 1 1 0 Clock 4 Clock 5 Clock 6