Set undriven outputs to VCC / GND

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There used to be, and you should NEVER EVER use this option.

Why? Consider the case where you have a board with lots of I/Os connected to external devices, eg., a processor. Now lets say you create a "blinky LED" design that uses the clock and LEDs, and you set all other I/Os as driven to VCC or GND.

Q: What do you think happens to your board when you configure the FPGA?

A: It powers up ever so briefly before the driver conflicts on the FPGA and the external devices cause the FPGA to get so hot that it is destroyed.

Yep, I learnt this one the hard way. The precursor to Quartus (MAX+Plus II) had the default to drive unused I/Os to ground.

I repeat NEVER EVER define unused I/Os as GND/VCC!

Cheers,

Dave

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Ok, thanks Dave.

So, the only option to avoid a weak glow of LEDs on my DE1 terrasic card is to set to '0' the corresponding ports programmatically (e.g. in "Initial" section or with "assign") ?