Queries regarding PCI with Spartan3

hi there,

i have been designing a pci target using spartan3 for some time. i m a new comer to this field and i have got some queries regarding the fpga configuration and its voltage requirements -

the motherboard that i m going to use, has 5V connector for sure. so i suppose the i/o s are 5V. now the spartan3 specifies its VCCO as 3.3Vmax. can this configuration of 5V pci and 3V spartan3, work reliably? are there any added precautions to be observed?

in the pci pinout, jtag pins are seperately specified. can i use these pins for configuration of the fpga? if so, can somebody suggest me a method/algorigthm/source code/software/link for this? has somebody used this before? in general, how can one address the jtag pins of pci target in windows or linux?

what throughput can i expect from the data acquisition system that i m going to put on the pci target card? i will be simultaneously using a modem, sound card, ethernet card.

will the operating system that i m going to use (windows or linux) have any bearing on the throughput? if yes, then if i program the card with its own operating system that is configured to work only with the acquisition card(i.e. if other pci cards are virtually rendered dead temperorily), will it improve the results? TIA, Shreyas Kulkarni

Reply to
Shreyas Kulkarni
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hi there,

i have been designing a pci target using spartan3 for some time. i m a new comer to this field and i have got some queries regarding the fpga configuration and its voltage requirements -

the motherboard that i m going to use, has 5V connector for sure. so i suppose the i/o s are 5V. now the spartan3 specifies its VCCO as 3.3Vmax. can this configuration of 5V pci and 3V spartan3, work reliably? are there any added precautions to be observed?

in the pci pinout, jtag pins are seperately specified. can i use these pins for configuration of the fpga? if so, can somebody suggest me a method/algorigthm/source code/software/link for this? has somebody used this before? in general, how can one address the jtag pins of pci target in windows or linux?

what throughput can i expect from the data acquisition system that i m going to put on the pci target card? i will be simultaneously using a modem, sound card, ethernet card.

will the operating system that i m going to use (windows or linux) have any bearing on the throughput? if yes, then if i program the card with its own operating system that is configured to work only with the acquisition card(i.e. if other pci cards are virtually rendered dead temperorily), will it improve the results? TIA, Shreyas Kulkarni

Reply to
Shreyas Kulkarni

There are plenty of references at xilinx.com about this. You will not like what you find out.

The PC motherboard market being what it is (very very price sensitive)I will be surprised if you find any motherboard that connects these pins to anything.

As a target only you might get 20MBytes/sec if you are very lucky.

Reply to
colin_toogood

Hi

You can't connect the spartan 3 pin directly to 5v.

I've a board that works fine on all motherboards i've tried and that uses TI SN74CBTD16211 between all the pci lines and spartan 3 pins

formatting link

It basically "clamp down" the mother board 5V signal to 3.3v level.

3.3v level generated by the spartan3 are not raised to 5v but it's ok.

For eg : you just tie the OE# to ground, VCC to 5V, and then uses A side for PCI and the B side for Spartan 3 (check the specs).

I don't think so. So far I've never seen theses accessible but they may be ... I would recommand another mechanism, more compatible with xilinx tools or xc3sprog ( // cable programmer for linux )

Depends of a lot of thing ... First the usage all theses devices (or other devices on the PCI that you don't see because hidden in the chipset or on the motherboard) do on the PCI Bus. With the FPGA you can try to measure the "busy state" of the bus.

Then it also depends on how your PCI target core works (how many cycle did he waste in pauses, does it support burst or force the master into retries, ... )

It will also depends on the way the master access the PCI bus, with single read/write, bursts, ...

Finally it probably depends on others thing I don't think of now.

One would guess so ... But if both operating system support your hardware well, the os difference should not be much.

BUT it will certainly depends on the way the driver for your card is written ... If you do a loosy job programming it then it will perform poorly. Basically, ensure what you do results in bursts !

Of course, if you don't do any other activity on the bus that will perform better but just not using thoses devices of disabling them would be enough, no need to write your OS !

It's a FPGA so if you already have the hardware (or any FPGA board with a PCI interface), you can do tests, see for yourself. For eg, count how many clock cycles the DEVSEL line is asserted during a fixed time (or clock cycle) and display it on some I/O, that should give a (rough ...) busy percentage of the bus.

Sylvain

Reply to
Sylvain Munaut

thank you Sylvain mentioning the IC number.

i would have definitely burnt my spartan3 if i wouldnt think about this.

now i can only hope that it is available in the markets nearby (TI is not sampling that one directly). thanks anyway for the help.

regards, Shreyas Kulkarni

Reply to
Shreyas Kulkarni

As you probably know, PCI cards support 3 different formats, 3v, 5v and both 3.3v and 5v. It depends on the keying of your card. If you want to use the spartan 3 FPGA in a 3.3V configuration only, you should design a

3v PCI card. This is determined by the keying of the card.

Note: Many of the newer computers can ONLY accept 3.3V PCI or UniversalPCI cards.

Hope this helps Ben

Reply to
Ben Popoola

that's right. but if ur motherboard is having 5v pci slots, then a 3.3v key will not fit into it.

my board has a 5v one, yet i want to use spartan3. hence the bus switch

- SN74CBTD16211. as Sylvain has mentioned, this ic converts 5v logic level to 3.3v which are perfect for spartan3.

regards, Shreyas

Reply to
Shreyas Kulkarni

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