![]() ![]() The 3 input AND gate will give a HIGH output when the counter reaches binary 7 because Q 0 is HIGH, Q 1 is HIGH and Q 2 is HIGH. All outputs go LOW and the count resumes from 0 on the next clock pulse. The timing diagram shows Q 1 go momentarily HIGH which causes RESET go momentarily HIGH on the 6th rising edge of the clock. The binary output 6 exists only as long as it takes the flip flops to reset. The output from the AND gate goes HIGH and immediately resets all the D-Type flip flops. On the next clock pulse the counter advances to binary 6 ( 1 1 0) such that Q 0 is LOW, Q 1 is HIGH and Q 2 is HIGH. The circuit shown starts from 0 and counts to 5. To make the counter count to a smaller maximum value, use logic to RESET the counter at a particular value. A 3 Bit counter can count 8 clock pulses with the outputs representing binary 0 to binary 7.Ī 3 Bit counter will count 8 counts (from 0 to 7). With all the outputs starting LOW (as shown) it takes 8 (2 3) clock pulses to return back to the same state. The timing diagram shows the state of the three outputs Q 0, Q 1 and Q 2Įach output stays HIGH or LOW for twice as long as the previous output. On the 4th rising edge of the CLOCK, Q 0 goes LOW and Q 1 goes LOW representing binary 0 0 and the count starts again.Įxtra Bits are added by adding extra divide by 2 counters with each counter being driven by the Q output of the previous counter. On the 3rd rising edge of the CLOCK, Q 0 goes HIGH and Q 1 remains HIGH representing binary 1 1 On the 2nd rising edge of the CLOCK, Q 0 goes LOW and Q 1 goes HIGH representing binary 1 0 On the 1st rising edge of the CLOCK, Q 0 goes HIGH and Q 1 remains LOW representing binary 0 1 Initially Q 0 and Q 1 are LOW representing binary 0 0 If Q 0 goes from HIGH to LOW, Q 0 will go from LOW to HIGH which is the required rising edge. therefore the CLOCK of the second divide by 2 counter must come from the Q 0 of the previous counter. Important: The second divide by 2 counter must receive a rising edge clock pulse when the output of the previous counter goes from HIGH to LOW. The next clock pulse makes the output go LOW again. When 1 clock pulse has been received the output will be HIGH. After the circuit has been reset the output will be LOW. ![]() This counter can only count from 0 to 1 i.e. To help understand how a Binary Counter works it would be useful to read about the Divide by 2 Counter on the D-Type Flip Flop page and about Binary Numbers. Due to circuit building conventions, the output of a binary counter circuit has the LSB output on the left and the MSB output on the right hand side. Note: When a binary number, such as 0111, is written down the LSB (Least Significant Bit) is on the right and the MSB (Most Significant bit) is on the left. The outputs from the binary counter represent 0 when they are LOW and 1 when they are HIGH. A binary counter counts clock pulses and the output is in binary.Ī binary counter is made from D-type flip flops configured as divide by 2 counters because each output is worth twice as much as the previous one and therefore should require twice as many clock pulses to make it go HIGH. ![]()
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