a pci implemenation problem, thanks

disabled)

read/write

Hi,

I'm currently working on a PCI target. The BARx registers are assigned there values by the BIOS, not Windows. You might already know this, but the BARx registers are either for memory mapped space (mem read/write PCI commands) or i/o port space (i/o read/write PCI commands). The first bit of the BARx registers identifies which type of memory you want (e.g. you hardwire the first bit). First the BIOS tries to set the bits in the command register and if it can set bits 0 and 1 it will then try and set the relevant values in the BARx registers. If you're not supporting either of the I/O or memory read/write PCI commands, the BIOS will not bother writing values to the BARx registers.

Does the BIOS try and perform an I/O or memory read/write command, just to check the device is working correctly? I don't know the exact answer to that, but I can't see why it would.

I would advise implementing the read/write commands. You don't have to do anything with the data. All you need to do is assert FRAME and TRDY. Discard any data you receive and only ever send out 0xFFFFFFFF.

Hope that helps,

The lower bits of the BAR are what tell the BIOS that it is active and should be used. You must set them properly.

No, the BIOS won't write there.

I have implemented the read/write operation, but I still cant get the bar assignment:( there is some problem: I can see my card under windows (but bar0 not assigned), but I can not see the card by BIOS. ( from the table on the screen after POST before boot OS) what's the problem?? BTW: I dont implement the interrupt pin.

Thanks Greg and Ben, I finally made it work. The problem is, I should remove the parallel download cable from the board before rebooting :P Thanks again!