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Cyclone III warning 16 pins must use external clamping diodes.

Altera_Forum
Honored Contributor II
‎05-25-2010 03:23 AM
1,566 Views

Hi, 

 

I just started noticing this Quartus message. I am using a Numonyx/Intel P30 flash chip running 2.5V IO for both cyclone 3 and flash chip. I didn't add clamping diodes to my hw design. Its kind of annoying to find out now because I followed the data book diagram which does not show any external clamp diode. Is clamping diodes necessary for flash configuration programming even if both CIII and flash are using 2.5V IO? 

 

Thanks for any help. 

 

Warning: Following 16 pins must use external clamping diodes. 

Info: Pin FLASH_DQ[0] uses I/O standard 2.5 V at N7 

Info: Pin FLASH_DQ[1] uses I/O standard 2.5 V at F4 

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Altera_Forum
Honored Contributor II
‎04-19-2011 08:38 PM
698 Views

I would love to see an answer to this question.

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Altera_Forum
Honored Contributor II
‎04-20-2011 07:21 AM
698 Views

The answer is in AN447 and similar publications, Altera expects signal overshoots exceeding safe voltage limits if no clamp diodes are used. If this actually happens depends also on the trace lengths.

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