PCI Configuration Registers accessed by 3rd device and not PCI Host

["Srividya Viswanathan" <srividya.viswanathan@idt.com>]

Hello PCI Experts

I am looking at a Dallas Semiconductor design which has a local bus and a
PCI Bus. The local bus has 2 modes

1) Normal/ Bridge Mode
In this mode, the PCI Host initializes all device specific config. registers
and PCI Config registers.
The PCI Host can access any  memory on the local bus (from the PCI bus - to
device - to local bus).
Application data transfer happens between the device and Host Memory through
PCI bus.

2) Configuration Mode
In this mode, the local CPU initializes all device specific config registers
AND PCI CONFIG. REGISTERS.
In this case, the IDSEL of PCI bus is disabled. The PCI Host cannot access
the device at all.
Application data is still transfered between the device and host memory
through PCI Bus.

My questions are regarding the Configuration Mode and the local CPU
accessing the PCI Config registers

1) Is accessing of PCI Config registers by a 3rd party a common practice?
2) Does it confirm to the PCI/PCI-X specification? Especially since IDSEL is
"disabled".
3) What happens if the PCI Host does initiate a PCI Config. Cycle to the
device?

Any help will be appreciated.
Please reply directly to me

Regards
Vidya
--
Vidya Viswanathan
IDT Dallas Design Center,
Ph: 972-244-2141