"ERROR: [DRC LUTLP-1] Combinatorial Loop Alert: 2 LUT cells form a combinat

0

Hi ,

I am creating a project in which oscillators are involved . I do the implementation on my system and then create the tar file and upload it to the AWS instance for AFI image creation.
But it throws the following error :
" ERROR: (DRC LUTLP-1)Combinatorial Loop Alert: 2 LUT cells form a combinatorial loop. This can create a race condition. Timing analysis may not be accurate. The preferred resolution is to modify the design to remove combinatorial logic loops. If the loop is known and understood, this DRC can be bypassed by acknowledging the condition and setting the following XDC constraint on any one of the nets in the loop: 'set_property ALLOW_COMBINATORIAL_LOOPS TRUE (get_nets <myHier/myNet>)'."

I tried setting the property as suggested above in the error comand but still i am not able to bypass this DRC error.

Any suggestions on this issue?

Thanks
Prigish

prigish
질문됨 5년 전558회 조회
3개 답변
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I think they banned combinational loops.

SamTian
답변함 5년 전
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Correct. We prohibit combinatorial loops.
Thanks
Kris

Edited by: awskrisk on Mar 10, 2019 3:25 PM

AWS
답변함 5년 전
0

Thanks for the response Kris and Sam.
So are you suggesting that there is no way in which this DRC check can be bypassed .
Combinatorial loops are formed since we are trying to integrate an IP which has got ring oscillators in it .

Regards
Prigish

prigish
답변함 5년 전

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