Page 53 - CITS - Electronic Mechanic - TT - 2024
P. 53

ELECTRONICS MECHANIC - CITS


           Truth table for simple decade counter

                                        Clock pulse     Q3      Q2     Q1     Q0

                                             0          0        0      0      0

                                             1          0        0      0      1

                                             2          0        0      1      0


                                             3          0        0      1      1
                                             4          0        1      0      0


                                             5          0        1      0      1

                                             6          0        1      1      1

                                             7          0        1      1      1

                                             8          1        0      0      0

                                             9          1        0      0      1

                                            10          0        0      0      0
           Decade counter circuit diagram


















           We see from circuit diagram that we have used nand gate for Q3 and Q1 and feeding this to clear input line be-
           cause binary representation of 10 is 1010
           And we see Q3 and Q1 are 1 here, if we give NAND of these two bits to clear input then counter will be clear at
           10 and again start from beginning.
           Important point: Number of flip flops used in counter are always greater than equal to (log2 n)  where n=number
           of states in counter.





















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                                    CITS : E & H - Electronics Mechanic - Lesson 9 - 29
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