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LukiLeu's avatar
LukiLeu
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4 months ago

Quartus crashes on long carry chain in Agilex 5 FPGAs

We try to manually place a carry chain in the Agilex 5 FPGAs which consists of more than 40 LABs. When we place this carry chain using set_location_assignment, Quartus crashes during the placement ph...
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ZiYingE_Altera's avatar
ZiYingE_Altera
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2 months ago

Hi LukiLeu​, 

I am Zi Ying and am currently assisting Kenny with this support ticket while he is out of the office.

I also heard from Kenny about your bike accident. Wishing you a smooth and speedy recovery.

Based on feedback from our internal engineering team, Agilex 5 supports approximately 46 to 47 LABs within a single continuous sector. As such, a single uninterrupted 50-LAB carry chain is not expected to fit on this device.

To help us determine the best next step, could you please confirm the minimum continuous carry-chain length required for your TDC to meet its reliability and accuracy targets? For example, would 43 LABs as your original design be sufficient, or is a chain close to 50 LABs essential?

This information will help us determine the most appropriate workaround for your design.

Thank you!

Regards, 
ZiYingE_Altera

LukiLeu's avatar
LukiLeu
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2 months ago

Hi ZiYingE_Altera​ 

The 43 Labs we use at the moment are generated by splitting the chain after 40 elements and thus this introduces a "large" delay there. So, with one continuous line, we probably need more than 43 LABs, 47 might be enough, but we would need to test and measure it.

The longer the chain can be, the better :-). But we would be happy to test it out also with 46-47 LABs (which would already help).