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AR# 41922

XAPP1014 - Why is the mode not locking correctly, or becoming stuck at HD-SDI?

Description

Why is the mode not locking correctly, or becoming stuck at HD-SDI?

Solution

This problem has been seen when XST encodes themode_int" FSM in triple_rate_rx_autorate module as a one-hot state machine. XST Safe Implementation should ensure that it never ends up in an illegal state, but in some cases this does not happen (for example, if a user adds another state to detect another mode like ASI).


The way to work around this is to force the encoding method using the fsm_encoding attribute in the source code.

(* fsm_encoding ="user" *) reg [1:0] mode_int = 2'b00;

This does have the side affect in that it may make it harder to meet timing, but this will keep the state machine from ending up in an illegal state.

AR# 41922
Date Created 04/26/2011
Last Updated 12/15/2012
Status Active
Type General Article