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Altera_Forum
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17 years ago

safe state machines

Hello, In the past, Altera recommended (in an older version of the Quartus handbook) to always explicitly specify the default state of state machines, to ensure that whenever a state machine ju...
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Altera_Forum
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17 years ago

Safe state machine option wasn't yet available with Quartus V5, so it can't play a role in the said document.

I don't have the May 2005 version of the Quartus Handbook, but I found the same statement in the previous December 2004 edition. In October 2005, (with Quartus V5.1) the chapter was completely edited. Particularly the limited effect of a default statement had been clarified:

--- Quote Start ---

Synthesis tools remove any logic generated by a default state if it is not reachable by normal state machine operation.

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According to a more recent revision history, your May 2005 version is reflecting Quartus V5.0 functionality. I doubt however, that Quartus V5.0 is behaving different regarding default state.