Forum Discussion

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

Unused CPLD Pins

I have two CPLDs on my PCB that connect to a common SPI bus. In order to keep things simple I'm trying to talk to only one of the chips at first but I'm having some trouble with the voltages which le...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

--- Quote Start ---

I did not change it, actually.

--- Quote End ---

Which device are you using?

The setting is under:

Assignments->Device, Device and Pin Options button, Unused Pins

(which can be a tab or selection menu depending on Quartus version).

--- Quote Start ---

Does this mean that they are basically an output set to low?

--- Quote End ---

Yep.

Its a stupid default, which has been changed to a sane value for newer devices.

This is why I always define a top-level entity with every signal pin defined. Then the unused pins really are unused and the unused pin setting is of no consequence.

Cheers,

Dave