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Active 1 month ago. Viewed 54k times. Add a comment. Active Oldest Votes. Jack Jack k 27 27 gold badges silver badges bronze badges. Can one type always be converted to the other? Not from a theoretical point of view. This means that if you explode every state of your Mealy machine adding the specific input for every outgoing transition you can simulate the same behaviour also if it's conceptually different.
Any Mealy machine can be converted to a Moore one. Mealy to Moore would require splitting the each Mealy state into the number of inputs coming into it with different outputs.
So if a Mealy state has two inputs with two different outputs, you would split that one Mealy state into two states in the Moore machine where each new state's output would match one of the two transition outputs in the Mealy machine. For the reverse situation you would simply move the output of the state to the incoming transitions instead.
The present inputs are going to influence the outputs that are going to come after the next clock. Click here to learn how to transform a Mealy machine to a Moore machine and vice versa. Mealy Vs. Moore: A Comparison. Hence mealy circuits are preferred mostly. Interviewer generally ask about this glitch issue.
Thanks for raising the point. But I think the generation of glitch is other way around. There is a possibility of glitches in case of Mealy while Moore is a more stable model. There are two types of output-generating finite state machines and those are: Mealy Machine Moore machine Let us discuss Moore and mealy machine with Moore and mealy machine examples. Mealy Machines Mealy machines are FSM with an output value that is determined by the current state and input symbol.
Conversion from Mealy to Moore Machine Take a look at Figure 2 for a mealy system transformation chart. Conversion from Moore machine to mealy machine Step 1: Let us assemble all of the Moore machine states using all an empty mealy machine in Table 4.
Difference between moore and mealy machine The points that distinguish between a moore and mealy machine are highlighted in the table below. Mealy Machine Moore Machine The output is determined by both the current state and the current input.
The output solely determined by the current state. When the input logic on the current state is completed, the value of the output function is a function of the transitions and modifications. Mealy machines respond to inputs more quickly. They all tend to respond in the same way. More logic is needed to decode the outputs in the Moore model, resulting in longer circuit delays. They usually respond after one clock cycle.
Conclusion Hope this article has given a clear idea about the moore and mealy machine and the application of Moore and mealy machine. Request callback. IF we initial the system to state 0 for both machines, we should get the following results S1 S2 O2 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 The external logic should not have any knowledge of the details of the internals of the machines, but call the update function for each machine once giving it the inputs, and taking and storing the outputs, and not be have exposed the internal state except as it happens to be an output.
It should be possible to update either or both of the update functions to different logic and still have a working machine, without needing to change the external logic. I believe you are not correct. The inputs are always current. The issue is which state is used, the current or the previous.
I don't know if you know VHDL, but it has the concept of a sensitivity list. Any time an input to a non-clocked function is updated, that function is evaluated to calculate the output. In the case of a Moore machine the outputs would only be calculated when the present state changes, meaning AFTER being updated. For a clocked process it is evaluated on the appropriate clock edge. So the next state is calculated and passed onto the present state at that time.
If you want to utilize the Mealy model, then the software need to accommodate updating the output when the inputs change as well as when the state changes. However, in most uses in software it won't matter since the module is not run other than when a state change is considered - equivalent to the clocked process in VHDL.
If you want to produce the same effect of a Mealy machine in software, you need to evaluate the output function separate from the state changes A bit esoteric for most applications.
The reality is that a true Mealy FSM model is virtually never used in software. I follow your example until the final conclusion. I don't know what you mean by "It should be possible to update either or both of the update functions to different logic". What external logic??? Do you mean the software that invokes and connects the signals between the two machines? I'm not clear what issue you are trying to address.
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