Re: My Introduction / How PPB claim configtype1 cycles

[Shimon Rottenberg <shimon@mellanox.co.il>]

Hi,

In order to decide whether to claim a config type1 transaction,
the bridge compares the bus number, which appears on AD[23:16]
to the secondary bus number and subordinate bus number registers.
These registers are located in dword address 18h of the config
space header (note the header type is 01h for PPB).

If bus number == secondary bus number, then the transaction
is claimed and converted to a config Type0 on the secondary bus.

Else if bus number is less than or equal to the subordinate
bus number, the transaction is claimed and forwarded unchanged
as a config type1 transaction on the secondary bus.

Else the transaction is not claimed (no DEVSEL#).

Regards,

-- 
Shimon Rottenberg
Mellanox Technologies LTD.
mailto:shimon@mellanox.co.il



> 
> Hello all,
> 
> I am new on this mailing list and also new on PCI systems. I work at cellware
> broadband gmbh in Berlin for nearly 2 years.
> I go thru PCI-, PPB-, CPCI- and HotSwap-Specs and several books but there still
> are a couple of gaps in understanding.
> 
> At the moment we develop a 32bit/33Mhz PCI system with up to 16 devices.
> Therefore we use the 21150 PPB from Intel.
> My question is how does the bridge knows that it has to claim
> a configtype1 cycle and forward it to a secondary bus ?
> I found registers to setup prefetchable-, non prefatchable mem and io space but
> no registers to setup the configuration space area of the secondary bus.
> 
> Thanks in advance,
> Jürgen Klemt.
> 
> PS.: Special geetings to djay@netlab.hcltech.com