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Altera_Forum's avatar
Altera_Forum
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14 years ago

FSM not recognized

I'm using SynplifyPro as input for Quartus. the input is therfore a vqm file. Synplify has made a one hot encoding (real one hot).

When analyzing the statemachine with signaltab is shows an other state sorting (probably the quartus onehot).

When further analysing I saw that Quartus did not recognize the statemachines (it does when using the same vhdl I used as input for SynplifyPro).

Why doesn't Quartus not recognize the statemachines from a vqm input file?

Second question why does Quartus change the state coding (I would expect is only routes the input from synplify not optimizing anymore) from synplify?

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    1) State-machines are recognized at a high-level, i.e. analyzing a case-statement. The .vqm is a low-level netlist of LUTs/FFs, etc. Quartus can't see the same things. That being said, Synplify should have already done all the necessary state optimizations as well as downstream optimizations that Quartus would have done.

    2) I imaging Synplify is doing the Altera one-hot synthesis. The reason this is done is that all registers power-up to 0. "Altera one-hot" just means the first state is all 0s, and so when decoding the lsb, you just invert the decode, i.e. if it's 0 it's active, if it's 1 it's not:

    0000

    0011

    0101

    1001

    Synplify can't get around the initial state having to be all 0s. So I'm sure it does the same thing.

    (So I think Synplify is doing everything you want)
  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    The reason i thought it was quartus was when i looked in the rtl view in synplify i see a true one hot. I cant see the state encoding in the technology view ( i think).

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    The RTL view reflects the source, not what it gets synthesized too. It could probably get mapped to various SM encodings but still look the same in the RTL view.