![]() ![]() Icarus Verilog) will produce different simulation results with a blocking and a non-blocking assignment in the "flip-flop". Nevertheless, I think they explain why some simulators (e.g. some continuous assignments and always blocks. I am grateful to CC for pointing out that that the statements above taken out of section 5 of the standard only refer to the timing of update events, and do not imply literal equivalence between e.g. So the bottom line is that that the two instantiations of an ff in my example below are equivalent to a module with multiple always clauses, which everyone would agree is broken.Īdded after Clive Cummings answered the question: In turn, a continuous assignment is just an always block sensitive to everything. In particular, section 5.6.6 "Port connections" on page 68 says that unidirectional ports are just like continuous assignments. Section 5 "Scheduling Semantics" of the 1364-2201 Verilog standard explains what happens. I now think the paper is unlikely to be correct. Can someone please tell me what part of the standard says that cannot happen? Many thanks. The way I see it, it's possible that the value of tmp is updated before it is used by secondff, thus resulting in one flip-flop rather than two. ![]() I would like to know why this would continue to work correctly if two or more of these flip-flops were connected in series. The document won a best paper award, so I assume the claim is true. He says that the following code (page 12, simplified) is a correct implementation of a flip-flop often used in textbooks, even if not exactly the kind that anyone should use. I have read "Nonblocking Assignments in Verilog Synthesis, Coding Styles that Kill!" by Clifford Cummings. ![]()
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