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ALT_PLLRECONFIG block busy signal problem

Altera_Forum
Honored Contributor II
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I have implemented ALTPLL_RECONFIG megafunction using an454. I have used 6 mifs, 1 mux, 1 reconfiguration block, 1 reconfigurable pll and a simple state machine. 

 

The problem is whenever I run the code, the busy signal toggles. It stays high for 2 clock cycles and low for one clock cycle. Because of this, I was never able to program the pll. 

 

I am attaching the screenshot in order to make things easier. 

 

I have no idea what the problem maybe. I am waiting for assistance. Thanks.
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Altera_Forum
Honored Contributor II
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Whats the frequency of your scanclk? 

 

Thanks
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Altera_Forum
Honored Contributor II
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25 MHZ. Does it have a upper or lower limit?

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Altera_Forum
Honored Contributor II
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--- Quote Start ---  

25 MHZ. Does it have a upper or lower limit? 

--- Quote End ---  

 

 

max 100MHz.  

does your read_param, write_param, reconfig, and write_from_rom being asserted? "Busy" will get asserted if anyone of these pins are toggle high.  

 

din
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Altera_Forum
Honored Contributor II
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you are right, after initializing read and write parameters, the "busy" signal went low, producing a suitable output.  

 

This point is not declared explicitly in the application note, I hope ALTERA stresses this detail in the next coming version of the application note.
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