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667 Views
Registered: ‎10-06-2017

Calling a presynthesized function from top level affects the latency numbers

Hi,

  We are having a top level function order_book_top() which calls another function insert(). When insert() is synthesized independently it gives latency of 34 clocks.  When insert() is called from order_book_top() the latency when viewed in analysis view changed to 68 clocks. However when we give data flow directive at the order_book_top(), latency remains 34 clocks. What could be the reason for this and how do we ensure that the latency of a function does not get affected when it is called from top level function.

 

awaiting reply,

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2 Replies
Xilinx Employee
Xilinx Employee
640 Views
Registered: ‎03-24-2010

Re: Calling a presynthesized function from top level affects the latency numbers

Check the synthesis report(*.rpt) or analysis view for insert in two situations to find any hint. For example, if there's a loop that II=1 when synthesizing seperately. However, the loop II=2 when it's in order_book_top, due to some dependence.

Regards,
brucey
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599 Views
Registered: ‎10-06-2017

Re: Calling a presynthesized function from top level affects the latency numbers

yes, II is changing from 1 to 2 when the function is called in the top level. Is there any way to keep the latency of the subfunction same when it is called from the top level? Is some directive available for doing this?

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