I'm trying to convert a flow chart simple state machine into Verilog code. But I'm somehow stuck with the following, and as I have hardly any knowledge in Verilog I'm probably missing something. Yes I had been intending to make an update to this page for while, especially about your first point on waveform display of the state vector. And this case we've got a pyramidal table that creates a binary set of values for each state, in addition to the clock, reset, the move inputs. Specifically, in EECS150, you will be designing Moore machines for your project. Post was not sent - check your email addresses! <>

Finite state machine (FSM) is one of the first topics taught in any digital design course, yet coding one is not as easy as first meets the eye. After simulating my coworker’s code in the original coding style, I also realized simulators do not visualize state vectors written this way very well. Thoughts and opinions expressed in articles are personal and do not reflect that of Intel Corporation in any way. So I guess having the default “next[IDLE]=1’b1” is probably not that useful here. You’re correct that in Cliff’s paper the enumerated type is used as an index into the one-hot vector. Verilog for Finite State Machines Strongly recommended style for FSMs Works for both Mealy and Moore FSMs You can break the rules But you have to live with the consequences Sprint 2010 CSE370 - XV - Verilog for Finite State Machines 1 Spring 2010 CSE370 - XIV - Finite State Machines I 2

However, I have coworkers who code in the way you suggested as well.There is a subtle point that may cause your code to not behave in the way intended. //} state, next; // Original not completely correct codeClick to email this to a friend (Opens in new window)One-hot State Machine in SystemVerilog – Reverse Case Statement I believe with today’s compiler technology it should synthesize the same as the reverse case statement method (i.e. Do you have another coding style or synthesis results to share? So let's examine verilog code for a binary encoded version of a state machine. I believe the correct code would look like this:with the vector declaration in place the rest of the example above should work OK.Hi John, thanks for your comment! r66=i9�����0�Q@J���]����[�S&J��!F�0�=��Z^ы�Kj�6 r �$��߁A�i�%�A��_�BN�

Let us consider below given state machine which is a “1011” overlapping sequence detector. Recently our team has turned on the Synopsys VCS x-propagation feature to detect this kind of problem. A one-hot state machine is generally faster than a state machine with encoded states because of the lack of state decoding logic. I understand your reasoning to have a valid case (like IDLE) be the default transition for safety. �� � �Ǽ�����d��l�Z]�����O8d&���w~�@ �a=7��r�

When you say the code “kills x-prop”, I think you mean that if “ws” or “go” input has the value of X, then the “if(x)-else” coding style will take on the “else” case, rather than also corrupting the outputs (in this case the “next” vector)?

Output becomes ‘1’ when sequence is detected in state S4 else it remains ‘0’ for other states. Unlike System Verilog, Verilog doesn’t have the ‘unique’ keyword.Put in another way, the question is what really happens when one codes a reverse case statement in Verilog with no ‘parallel_case’ directive. Due to the use of “unique case” in the code, I think for any unspecified cases (e.g. This is a Verilog example that shows the implementation of a state machine. 5 0 obj Killing x-prop can cause “simulation vs. synthesis mismatch”, which can be pretty fatal. Personally I don’t code that way as I think a bit flip anywhere in the chip is considered fatal, and even if the affected state machine returns to IDLE, it will likely have become out of sync with other logic and state machines. I would agree that specifying the one-hot state encoding in the enum type should be equivalent and will display better. That would not kill x-prop anyways since the default in the case statement would override it if needed.Thanks for your comments! This page covers Mealy Machine Verilog Code and Moore Machine Verilog Code.. Mealy Machine Verilog code.