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Errorr simulating in Quartus (Zero-time oscillation in node)
Hello everybody. I'm doing block control cache for study project and I have some problems when I use a functional simulation. Process of functional simulation never ending and show many errors: Error: Zero-time oscillation in node "|MAIN_MODULE|CACHE_BLOCK:inst5|CACHE_CONTROL:inst1|lpm_mux:Mux49|mux_ric:auto_generated|_~1094" at time 27.5 ns. Check the design or vector source file for combinational loop. Error: Zero-time oscillation in node "|MAIN_MODULE|CACHE_BLOCK:inst5|CACHE_CONTROL:inst1|lpm_mux:Mux49|mux_ric:auto_generated|_~1145" at time 27.5 ns. Check the design or vector source file for combinational loop. ... I's at 6 min after start simulate and simulation process is still in progress. I use Quartus 9.1 Web Edition. Here is VHDL code, where Quartus show errors: cache_control.vhd (http://www.alteraforum.com/forum/attachment.php?attachmentid=7964&stc=1&d=1382735658) I'm level beginner with VHDL and cannot find, what I'm doing wrong. Can anybody help me with this? Here is link for whole project if it need I cannot attach it to post, cause it 3 mb more then max file size attach.Link Copied
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A logic loop is when X = f(A,X), ie. the output is a function of itself. So I assume you have generated a couple here.
Is there any reason you have not created a synchronous circuit?- Mark as New
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--- Quote Start --- A logic loop is when X = f(A,X), ie. the output is a function of itself. So I assume you have generated a couple here. --- Quote End --- Thank you very much, I fix it and everything works ok. --- Quote Start --- Is there any reason you have not created a synchronous circuit? --- Quote End --- Yes, some other blocks work asynchronous.
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With asynchronous code you risk all sorts of timing problems (temperature problems, race conditions etc). I would highly recommend you make as much of the code synchronous as you can.
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