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

Altera_Forum
Honored Contributor II
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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 in google using level shifter IC between FPGA I/Os and PCI connector, but some connect to PCI connector directly. Actually,i am not really understand about that. Please help me ? Thanks so much!
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Altera_Forum
Honored Contributor II
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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
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Altera_Forum
Honored Contributor II
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Dear Dave, 

Thanks for your reply,really useful for me. So if i do not need hot swap function, i can interface FPGA I/Os to PCI connector directly . Because i keep my design is so simple if possible,because PCI is just a communication protocol. I wonder,if PCI 5V system output 5V to Input pin of FPGA (with VCCIO=3V3) can damage FPGA I/Os? 

About PCI and PCIe,i use Low Cost Cyclone II TQFP so i think Cyclone II do not support PCIe link without TI PHY serdes chip , and maybe Driver is more complex too. 

Best, 

Hoang Nguyen
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Altera_Forum
Honored Contributor II
503 Views

 

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So if i do not need hot swap function, i can interface FPGA I/Os to PCI connector directly. 

 

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You can not interface to the PCI connector directly - p108 of the data sheet ... 

 

http://www.altera.com/literature/hb/cyc2/cyc2_cii5v1.pdf 

 

shows that Cyclone II are not 5V tolerant. 

 

 

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Because i keep my design is so simple if possible,because PCI is just a communication protocol. 

 

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No its not. The PCI interface is power and communications. It is not that simple. The power sequencing on your board is influenced by the motherboard. It is important that you include a hot-swap controller and MOSFETs on the board to ensure that the power turns on on the board in a sequence you define. For example, on these boards here: 

 

http://www.ovro.caltech.edu/~dwh/correlator/index.html 

 

I used a PLX PCI9054 PCI-to-local bus bridge as the PCI interface, and a FLEX10K FPGA as the system controller. The FLEX10K configures from an EPC2 EEPROM. There is absolutely nothing in the data sheet about power sequencing requirements for the EPC2. However, if the 5V and 3.3V power on the cPCI backplane does not come on simultaneously, then this board will not configure. That was my lesson in learning that as the board designer, if I want to ensure that power is sequenced how I want, regardless of the power sources, that I need to use a hot-swap controller to ensure the sequence. My advice to you is to follow it - you can ignore it ... but later on if you have problems I'll just say "I told you so" :) 

 

 

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I wonder,if PCI 5V system output 5V to Input pin of FPGA (with VCCIO=3V3) can damage FPGA I/Os? 

 

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Don't wonder. Read the data sheet, its right there on p108. You will damage the I/O. 

 

 

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About PCI and PCIe,i use Low Cost Cyclone II TQFP so i think Cyclone II do not support PCIe link without TI PHY serdes chip , and maybe Driver is more complex too. 

 

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What is low cost about this part? A Cyclone IV GX is not too expensive: 

 

http://www.altera.com/products/devkits/altera/kit-cyclone-iv-starter.html 

Cyclone IV GX EP4CGX15BF14C8N 

http://www.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=ep4cgx15bf14c8n 

 

Actually, as part of the "Bigger Picture" why are you designing a board anyway? That is not really a masters level project, that is more a means to an end. What do you want the board for? 

 

Cheers, 

Dave
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Altera_Forum
Honored Contributor II
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Dear Dave, 

I understood it already , your advice is so good for me. Maybe i will change the design according to your comments. 

About the project, I want to design the data acquisition Card using FPGA for high speed data. 

Thanks so much!I am sorry if i will disturb you again, in the future :) 

Best regards, 

Hoang Nguyen
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Altera_Forum
Honored Contributor II
503 Views

 

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Maybe i will change the design according to your comments. 

About the project, I want to design the data acquisition Card using FPGA for high speed data. 

 

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Why don't you try and describe the project requirements in a little more detail? 

 

Why design a high-speed data acquisition card if you can buy one? 

 

What is the "real" objective of your masters project? That is, what are you going to measure with this high-speed ADC board? 

 

Read through the documents on this page: 

 

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

 

This is a high-speed data acquisition card with dual 1GHz ADCs, lots of FPGAs, and a PowerPC processor. I had to design this board as I could not buy one that met my I/O requirements. 

 

Designing a board containing both analog and digital requires great attention to detail. It requires more than just slapping a few parts down and hoping it will work. Since you are a masters student, you likely do not have any experience in this area. If your advisor does not either, then your first attempt will likely fail. If you have an application that requires a data acquisition board, then buy one, and *learn* from that design. Then build your own if you need to. 

 

Cheers, 

Dave
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Altera_Forum
Honored Contributor II
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i just want to design a normal high-speed DAQ card (50Mhz sampling ADC). And ofcource i can buy it easily, But i want to make own design instead of buy anything. I just work on RTL before, so design the FPGA PCB is new for me.

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Altera_Forum
Honored Contributor II
503 Views

 

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i just want to design a normal high-speed DAQ card (50Mhz sampling ADC). 

 

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What you "want" to do versus what you "need" to do to graduate with a masters may be two entirely different things. You'll have plenty of time to work on PCBs once you are finished your masters. 

 

Find out from your supervisor whether or not such a board design would be considered sufficient for your masters degree. If it is not, then find out what is required. 

 

As I comment above, there is a lot of stuff to learn, but if your supervisor is not familiar with this type of design, you will not learn much. You need to select a topic where your supervisor can actually help you out.  

 

Cheers, 

Dave
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Altera_Forum
Honored Contributor II
503 Views

 

--- Quote Start ---  

What you "want" to do versus what you "need" to do to graduate with a masters may be two entirely different things. You'll have plenty of time to work on PCBs once you are finished your masters. 

 

Find out from your supervisor whether or not such a board design would be considered sufficient for your masters degree. If it is not, then find out what is required. 

 

As I comment above, there is a lot of stuff to learn, but if your supervisor is not familiar with this type of design, you will not learn much. You need to select a topic where your supervisor can actually help you out.  

 

Cheers, 

Dave 

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OK,i got it.Thanks for your advices !
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