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Altera_Forum
Honored Contributor I
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Altera MAX10 enable clock-buffer primitives without synchronization?

Irrespective of the relative evil of gating clocks in FPGAs my understanding was that one should synchronize the enable signal to the clock being gated by means of a flip-flop chain.  

 

 

However, while studying the documentation for the MAX10 device I stumbled over the following section: clock enable signals (https://www.altera.com/documentation/mcn1395213337540.html#mcn1395926825834) where the figures 5 and 6 seem to indicate that no synchronization seems to be necessary.  

 

 

https://i.stack.imgur.com/hffeq.png  

 

(https://i.stack.imgur.com/hffeq.png

 

https://i.stack.imgur.com/n5b4c.png (https://i.stack.imgur.com/n5b4c.png

 

 

Do I miss something? 

 

Moreover, how should I constrain a gated clock?
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Altera_Forum
Honored Contributor I
76 Views

I understand that there are no two stage registers but I believe the document meant to gate the clock with enable (generated from its domain) as per figure 5

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