Forum Discussion

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

Can Cyclone II I/Os interface PCI 3V3/5V directly ?

Hi, i want to design a FPGA cyclone II board with PCI universal 3V3/5V interface for master thesis. But i am worry about voltage of universal PCI spec,because FPGA I/O is 3V3. Some design i found ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

Its actually safer/better if you design your board as if you were going to support hot-swap (plugging the board in while the motherboard is powered). There are lots of motherboards that do not power-on their supplies in a particular sequence. Actually, I think I've probed some PCI motherboards that have either 5V or 3.3V, but not both, and others that have both.

Anyway, you should design the board to be 3.3V. You should design the interface to the PCI connector using busswitches. You are welcome to copy the design here:

http://www.ovro.caltech.edu/~dwh/carma_board/

This is a compactPCI interface, but if you look at the schematic, you'll see its much the same as PCI. The TI BusSwitches used in the design allow the board to be plugged into either a 5V or 3.3V backplane without damaging the 3.3V PowerPC. The hot-swap controller ensures that the PowerPC and FPGA supplies turn on in the right sequence.

Actually, PCI is pretty much dead. Why are you bothering with PCI? You'd be better off designing a PCIe board.

Cheers,

Dave