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Altera_Forum
Honored Contributor I
991 Views

Cyclone-V changing off-chip signal timing using IObuf delays

Because of routing differences in a bus system we want to experiment with input IO-buf delays of a cyclone.  

 

The D3_delay and D1_delay options in the quartus assignment editor are available but I do not know their value range and units (sec/usec/??). Does anyone has info on this.  

 

Performance improved when using FAST_INPUT_REGISTER assignment on the bus clock signal. Is this attribute the counterpart of D1/D3_delay or can these be combined?
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4 Replies
Altera_Forum
Honored Contributor I
55 Views

Refer to the 'Programmable IOE Delay' section, page 81, in the "cyclone v device datasheet (https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/hb/cyclone-v/cv_51002.pdf)". 

 

Cheers, 

Alex
Altera_Forum
Honored Contributor I
55 Views

You should use Fast I/O register assignment before resorting to buffer delays (which without looking at the document I think are usually in 50 ps increments). That makes the design use the input or output register located in the I/O block, the closest it can be to the I/O pin.

Altera_Forum
Honored Contributor I
55 Views

Thanks for the reference Alex. Do you also happen to know if these figures are the range or the step size of the parameters? 

 

Sstrell do you mean the FAST_INPUT_REGISTER assignment? Can this one be combined with an input delay like D3?
Altera_Forum
Honored Contributor I
55 Views

I've always assumed, and used it as if, it's the range - although finding a statement to that effect eludes me. Timing analysis is your friend here. 

 

Yes, you can use both together. 

 

Cheers, 

Alex
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