RE: PCI Clock arising problem

["Olaf Birkeland" <olaf@interagon.com>]

Hi,

If you also see a short period with active clock signal when FPGA is
inserted, then most probably the BIOS is not able to get anything sensible
when reading the config space of your PCI interface in the FPGA. It thus
thinks the slot is empty, and disables the clock.

Some motherboards also uses the PRSNT[2..1]# lines, and if none of these are
tied to ground by your card, it assumes an empty slot.

Reenabling the clock can (usually) be done in software, but is very
dependent on the motherboard implementation. Is there any PCI/PCI bridges on
the motherboard? If your behind an Intel/DEC 2115x bridge, the app notes
recommend using PRSNT-signals to disable clocks, without any BIOS
intervention. It can anyhow be reenabled by setting the correct register.

Regards,
- Olaf

> -----Original Message-----
> From: Mayank Sharma [mailto:mayank.sharma@wipro.com]
> Sent: January 09, 2003 13:06
> To: pci-sig@znyx.com
> Subject: PCI Clock arising problem
>
>
> Hi All ,
>
> I am using a PCI daughter card ,If I insert that card into 5V PCI
> Slot , PCI Clock is not seen in the Logic Analyzer or
> Oscilloscope , even if we remove the FPGA from the board
> .....then I see the clock comming up for a short time and then
> goes off ....afterwards.
>
> If I insert some other daughter card into this same PCI Slot , I
> can see the PCI Clock , comming to the board....
>
> Can any one help me out in knowing the possiblity of this clock
> problem I am facing
>
> thanks and regards
> Mayank
>