3 bit ripple counter vhdl code for digital clock

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Learn more… Top users Synonyms. Is this a new type of ripple counter? Ripple counters have output bits not change states in synchronism. On the other hand, synchronous counters have their bits connected to the same CLK pulse.

However, I ran into circuits, which I Thong Nguyen Thanh 5 1. What can I do to change the output count down into Evangelina Tessia P 18 3. Gehad Mohamed 12 4. Active high-active low for preset In a FF when clear is 0, output is also 0. So what should it be considered as? Active low or high clear? If it active low doesn't it mean that output should be 1? Propagation delay in asynchronous counter Are the ripple counters useful in real life?

Followings are the block and the waveform diagram: After the countit will appear This requires 2 BCD displays and N drivers to interpret the bits from the The Progenitor 18 3. Small doubt in asynchronous counter I was trying to understand the ripple effect in asynchronous counter and I came across this figure: I need a propagation delay that is at most ns. The best solution I The Quantum Physicist 7. Propagation delay in asynchronous circuit Consider the circuit shown below where delay of each flip flop is 10ns and delay of each AND gate is 5ns each.

What is the total propagation delay? Rajesh R 50 5. How to convert this into a down counter? My UP counter counts Ripple counter, reset problem J-K flip flop counter I am trying to simulate a decade counter using a ripple counter 4 bits and a NAND gate to reset the 4 J-K flip flops when it reaches 10 The thing is it does not reset but goes to 4 due It should count from 29 down Supa hot Fire 8 2.

Everywhere I encounter either asyncronous ripple counter binary counters or syncronous ones, the application uses JK flip flops with the J and K inputs tied together, such as described here: Alex Eshoo 4. Can you make an asynchronous counter count in Gray Code?

I will firstly explain my situation and then ask a few question in the clearest way possible. I am a total beginner and thanks for coping with me. I was given the task of designing a Sequential counter for repeating counting sequence I'm aware of designing synchronous counter design for a counting sequence where I write the state table with present and next state and then followed by flip flop inputs filled using the excitation Fawaz 99 1 1 8.

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He wondered if he could do the same on an FPGA, and how hard it would be to count high clock rates. The simplest solution for counting a clock would be to count a clock for a second with a huge, bit counter. This is a terrible idea: The solution is to have the input signal drive a very small counter — only five bits — and sample the counter using a slower clock on board the FPGA.

Because [Michael] is using a 5 bit clock with 31 edges sampled at 32 MHz, he can theoretically sample a MHz clock. There is annother interesting way to implement a counter like this, and that is to remove the adder from the critical path. Instead of carrying you keep two numbers that when added together make up the count, you can do this with only one full-adder per bit.

Or he could just have pipelined the counter. If we are talking about fast counters, then LFSRs should be mentioned: I was thinking of offering a prize for a faster Spartan 6lX9 design, where all it had to do was count the frequency of the incoming signal and squirt ASCII down any serial port.

However that would be unfair of me as it is the maximum switching rate of the clock buffer that is the limiting factor, not the programmable logic — as it should be the fastest design that passes timing.

The underlying logic of LFSRs are faster, but how do you cleanly transfer the state of the LFSR into your clock domain and then convert it back to a binary number? This makes LFSRs better four when you are 3 bit ripple counter vhdl code for digital clock to a preset terminal count then reseting. If you are counting frequency, you are essentially looking at the change in clock count over a period of time. Once the sampling period is over, you gate the input signal to stop the counter. Examine the bits and when you are done let sampling period starts again and the counter to do it work again.

Yes — you can gate the clock, but then you will need a long counter, 29 bits if you want to count for a second at up to MHz. To use that technique might have to use around a bit counter, and would need to pause it every us to read back the current count.

This would cause errors in the final total. If you make a simple asynchronous counter aka ripple counterthere is no carry as such; each bit toggles when the next lower bit goes from 1 to 0.

You can do that for later stages, but for early stages, clocking via local routing decreases greatly your maximum possible frequency.

Guess no one reads my comment just 1 comment below you. They used a chain of ripple counter. The clock-to-setup delay of 2. Now how much faster is the FPGA used again? If you can make a gray code counter at MHz to count your input, you have already a way to get that clock into the FPGA and toggle some logic inside. The part lacking is to think outside of the everything should be synchronous mindset.

BTW take a look at this: If they can measure MHz with the old XC, I am pretty 3 bit ripple counter vhdl code for digital clock that the same trick can be done on after so many generation of improvements. The clock speed limitation is a combination of the output delay, the 3 bit ripple counter vhdl code for digital clock delay, and the setup delay of a single CLB.

If you are already at the maximum frequency, then yes, there is little advantage to an LFSR. However, an LFSR will always be faster than a simple counter, even with a carry chain, as it only requires a single gate with two inputs.

The rest of the chain is just shift registers. You can even pack those shift registers into SRLs, up to a bits in a single slice but that limits flexibility. As far as reading it periodically, you can just clock it into a second set of registers periodically 3 bit ripple counter vhdl code for digital clock the high speed clock, then with a low speed clock pass it through logic for converting to numerals.

You can also do comparisons utilizing the high speed clock and a single LUT if you are comparing to a 6 bit constant, or using a series of LUTs 3 bit ripple counter vhdl code for digital clock a carry chain if you are comparing against a larger constant.

Counting the input clock and measuring its frequency are two very different things. Counting accurately is probably limited to around MHz easily. There are 12GHz prescaler these days. The chip is a bit hard to find though. Would you consider a follow-up with a focus on enhanced resolution? That would require tacking a few more digits to the display, of course. Well, there are other reasons to have a high frequency clock counter.

Time tagging, for instance. Getting the high-frequency clock counter is just the first part. Feed the clock into a carry chain that extends across the entire chip vertically. Periodically sample the output from the carry chain into flip-flops 4 for each slice.

Depending on the various noise and jitter sources, you now have a somewhat noisy image of the input signal frozen in time. So it is fine for resolving when the rising or falling edges on a relatively long e.

I had better luck with chaining carefully placed and routed LUT tables, configured as inverters. I managed to get better than 0. Apart from the very, very tricky layout and signal routing needed, the big downside of this technique is that the delay changes with operating conditions, so you need a reiable way to calibrate against a known signal. You are commenting using your WordPress. You are commenting using your Twitter account.

You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email. By using our website and services, you expressly agree to the placement of our performance, functionality and advertising cookies. Now that was a much better hack. At least not one straight off. Heckuva lot more work, though. Leave a Reply Cancel reply Enter your comment here Fill in your details below or click an icon to log in: Email required Address never made public.