Hello, I want to design 8x1 multiplexer. But, I just only have 5 options of input, which are freq1, freq2, freq3, freq4, and freq5. Is it possible to design it with only just have 5 options of input? Thank you.
Min_ah wrote: > Is it possible to design it with only just have 5 options of input? Its like dricng a car possible to speed up to 200km/h only with 125km/h... > Is it possible to design it with only just have 5 options of input? Yes, if you use only 5 inputs, then the remaining 3 are unused and tied to '0'. Or they are the "when others" case and mirror one of the selections... > 5 options of input, which are freq1, freq2, freq3, freq4, and freq5. You want to multiplex (clock) frequencies?
Min_ah wrote: > Multiplexe_8x1.docx (11.1 KB, 3 downloads) I'm sorry, I will not download a docx file. That is not a format to interchange documents. Try a pdf instead... > Yes, I want to multiplex clock frequency. Usually that is a very, very bad idea. If you are a beginner you should not do a design needing 5 different clocks. It will break your bones. To get a clearer picture write as much information as possible. What do you need thes clocks for? Are that really clocks? Where do the signals come from? Where do they go to?
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Multiplexer.JPG
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I need to design the Multiplexer like the picture I give above.
it's quite straight-forward to describe such a multiplexer in VHDL. When I google the words "VHDL multiplexer" pretty much every link I get gives a useable guideline. If I follow two or three links, then I even get a source which can get copied without much modification. But as Lothar already mentioned: multiplexing Clock signals in a real design will not work like that (even if the simulation may tell you something different). With such a Multiplexer you can deliver a logic signal Yout as output. But a logic signal and a Clock are something different inside an FPGA (they do not even share the same signal lines). If you want to run it in real hardware, then you'll need a different approach.
Min_ah wrote: > I need to design the Multiplexer like the picture I give above. This is (as already said) NOT a way to generate signals for use as a clock inside a FPGA. Instead I urge you to have a look for the clock enable strategy: only 1 clock (about 50..100MHz) throughout the whole design and then a bunch of signals generated by counters, each signal active for a single clock cycle.
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