The outputs of the 4040 switch between a logic “1” or “HIGH” and a logic “0” or “LOW” on each count so it can produce a moving sequence, chaser or random effect, making the 4040 ideal as a simple LED flasher or lighting display for a lights project.Īs the 4040 is a 12-bit ripple counter, each one of the twelve outputs will toggle HIGH or LOW in a binary sequence from 0 to 4096 (2 12), and this is shown in the following timing diagram. These twelve outputs switch sequentially on the arrival of each negative-going edge of the clock pulse producing a binary output sequence as shown in the timing diagram. The CD4040B is a fast switching 12-bit binary ripple counter complete with twelve fully decoded outputs (making a total of 12 individual LED sequence’s). So for example, output Q6 is 2 6 = 64 ( 1/ 64 of the clock frequency) and Q12 is 2 12 = 4096 ( 1/ 4096 of the clock frequency) and so on.Īs we have seen, there are many binary counters available that can flash any number of lights periodically, randomly or sequentially but one very versatile IC that the hobbyist or student can use to produce a simple LED flasher for use in a variety of different lighting displays is the CMOS CD4040B 12-bit Binary Counter. Then their output count, ( Qn) would be defined as the “N-th” stage of the counter. Ripple counters are constructed from a number of divide-by-2, T-type flip-flops cascaded together to form a single divide-by-N frequency divider, where N is equal to the counters bit-count. The result is a ripple effect as each stage changes in sequence and we can put this to good effect as a simple LED flasher circuit. The toggle or “T-type” flip-flop is the basic building block of all counters with asynchronous counters are commonly referred to as “ripple counters” because the input clock pulse appears to “ripple” through the counter as the clock input for one stage is generated from the output of the previous stage. Usually the toggling occurs on the negative edge of the clock pulse. These types of counters are asynchronous in nature because not all the flip-flops change or “toggle” together with the application of an external clock pulse. Ripple counters as we discussed in the Counters tutorial, are basically toggle flip-flops that can be used as frequency dividers to divide the reference clock input by a set amount to give a new, lower frequency and which we can use as part of our simple LED flasher design. Therefore, a bit counter can also be called a mod 4 counter.The electronics student or hobbyist’s always likes to make various circuits for their home or school and especially ones that flashes a few lights, and there are many circuits and kits on the market that can flash any number of LED’s or lights periodically, randomly or sequentially but one very versatile IC that can be used to produce a simple LED flasher circuit is called a binary ripple counter. Thus, for a 2-bit counter, there is a mod 4 counter by the mechanism of 2 to the power n. These numbers of states are asserted as mod numbers. Like the 2-bit counter, a counter having n number of flip-flops can have 2 to the power n states. There is the placement of each counter to correspond to the account value. The above two-bit ripple counter has four states. The clock pulse given into the first flip-flop is rippled through the other counters after the propagation delay. There is a small delay between the clock and the first and second transitions in the above counter.Īll the clear inputs are connected together so that a single pulse can clear all the flip-flops before the counting of bits. This phenomenon occurred here although it is an asynchronous counter. The transitions of Q 0, Q 1, and clock pulse in the figure of the timing diagram above are simultaneous. Therefore, the triggering of flip-flops cannot be simultaneous. Due to an essential propagation delay in the circuit through a flip-flop, the change in the input clock pulse and change of the Q output of the first flip-flop can never occur at the same time giving the exact result. But the second flip-flop changes only when it is triggered by the Q output of the first flip-flop. So, this is why the first flip-flop changes the state at the quick falling edge of the clock pulse. The external clock is connected to the clock input of the first flip-flop. Mechanism of working of 2-bit Ripple CounterĪ 2-bit ripple counter is shown in the above figure. We can use them as both Up and Down Counter. 2-Bit Asynchronous Counter is the type of ripple counter which has only 2 flip-flops in its design.
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