AR# 9401: 3.1i XST - XST selects one-hot encoding for state machines, regardless of what encoding was chosen.
3.1i XST - XST selects one-hot encoding for state machines, regardless of what encoding was chosen.
Keywords: WebPACK, encoding, scheme, XST, ISE, one-hot, Project, Navigator
General Description: I have selected Johnson encoding for my state machine when synthesizing with XST. After fitting the design, it appears as if the software has ignored the request and is using one-hot encoding instead.
From the report:
---- Other Options c : Johnson ... | Encoding | automatic ... Selecting encoding for FSM_0 ... Encoding for FSM_0 is One-Hot, flip-flop = D
The same thing happens if other encoding schemes are selected, and the problem is apparently not specific to any device family.