I have an old motherboard which has four pci slots. I want to use it as one pci output port. I would like to use pci interface as low frequency simple output. pci can work lower than 133/4 =33Mhz for example 133/16=8.3Mhz
no interrupt required, no handshaking. there wont be any register on target board so no device id no port no memory information.
is it possible to output data like this?
Off the top of my head, I can't see how this would be possible.
The PCI bus has handshaking signals that are required just to get data out onto the bus - the address is presented first and signals like FRAME#, TRDY#, DEVSEL# etc need to be driven correctly for the data phase of the transaction to begin.
But even before that, I can't even see how you'd get a transaction out onto the PCI bus in the first place?!? You won't have an address space assigned to your card so I guess you'd have to rely on unclaimed addresses being sent to the PCI bus??? Unless you can cleverly use PCI configuration cycles to do your I/O for you?!?
Other opinions?
Regards, Mark
It is, but it's not "really" PCI. Here's an example using an FPGA and Verilog: you could translate it to a CPLD or to discrete logic if you prefer. You'll have to find out what addresses the system already allocates to pnp PCI, and avoid those.
If you want something more "permanent" get hold of a PLX development kit and work from there.
Paul Burke
At boot time bios assign memory and i/o address to pci card. If there is no card it won't be assigned. But it is not necessary actually because hot-plug devices are configured after boot time. I wonder without any pci card installed can I send any data to pci bus. It's name is not important configuration i/o adress data whatever it is. Can I write to pci bus without any device installed ?
Another option :
I can install a any pci card into slot, it makes necessary negotiations. After some few milliseconds I write to this card but I tap 32 data lines from pci bus to my circuit.
At low speed I think there wont be signal integrity - impedance problems.
8.3 Mhz x 32 bit = 250 Mbit data is very usuful for me..What do you think is it possible ?
MY motherboard has onboard vga and ethernet. when these devices are used, is there any traffic on pci bus? does each device respond their own i/o adres ? or is there any other sinal whict selects target device? is 32 bit data signal broadcasted ? can all devices see transmission?
VGA, maybe or maybe not.
Ethernet, probably yes.
Yes.
On reset, PCI devices don't respond to any memory or I/O addresses; they only respond to accesses to configuration space. The BIOS or operating system configures the devices and assigns addresses. Once this is done, all you need to access the device is the appropriate address.
Of course, PCI protocol still requires arbitration and handshaking, which involves the IRDY, TRDY, and other PCI signals.
On any given bus it can be viewed as a broadcast, but you may have more than one PCI bus. For instance, the onboard Ethernet might be on the same PCI bus as the expansion slots, or it might not.
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