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Altera_Forum's avatar
Altera_Forum
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13 years ago

Cyclone IV not stable on my PCBs, completely stumped

I've got an EP4CE10F17C8 based design that I've recently moved from an Issue 1 PCB to an Issue 2 PCB, and now it's not behaving properly. Even a very simple configuration containing just a modulo 10 ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

Hi Oliver,

is the track for the clock identical in terms of corners and/or via? It seems like there is a disturbance by the clock signal reflection on the PCB... Or - even if this may sound stupid (and I have not yet checked if there is any effect on this) - the level configuration may mismatch, i.e. the Cyclone clock pin being configured as LVTTL 3.3 and your's oscillaltor being 3.0V type...

It is definitely strange, I've never had this with the CLK signal and dedicated CLK pins of Cyclone IV - I know this for external inputs used by state machines if these are not synchronized to clk before...