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Altera_Forum's avatar
Altera_Forum
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15 years ago

Cyclone III warning 16 pins must use external clamping diodes.

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. ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

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.