Cyclone III AS configuration problem (yes another)

What are your power supplies like, are they up to the job?

There is an inrush current on VccInt (on some devices) which can be >> normal operating current. If your supplies aren't up to this it might be

causing what you're seeing.

Also, how far away is the config device to the FPGA? Controlled impedance tracks?

Tracks with associated ground planes not crossing slots?

No long parallel tracks that could be coupling crosstalk?

I always place the config device and the JTAG header as close to the FPGA as possible (all else considered) on the assumption that reliable

configuration's the first step to producing a reliable board!

I'm also almost exclusively using JIC config from the JTAG header. This usualy allows shorter tracks all round.

Nial.