Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
69
Address Translation Unit (PCI-X)—Intel
®
81341 and 81342
2.2.1.4
Inbound Configuration Cycle Translation
The 81341 and 81342 ATU only accepts Type 0 configuration cycles with a function
number of zero when bit[7] of the ATUHTR (see
Section 2.13.11, “ATU Header Type
Register - ATUHTR” on page 158
) is cleared or function numbers of zero and one when
bit[7] of the ATUHTR is set.
The ATU is configured through the PCI bus. When operating in conventional PCI mode,
all inbound configuration cycles are processed as delayed transactions. When operating
in PCI-X mode, all inbound configuration cycles are processed as split transactions. The
translation mechanism for inbound configuration cycles is defined by the PCI Local Bus
Specification, Revision 2.3.
The ATU configuration space is selected by a PCI configuration command and claims
access (by asserting
P_DEVSEL#
) when the
P_IDSEL
pin is asserted, the PCI
command indicates a configuration read or write, and address bits
P_AD[1:0]
are 00
2
all during the address phase. The ATU interface ignores any configuration command
(
P_IDSEL
active) where
P_AD[1:0]
are not 00
2
(e.g. Type 1 commands). During the
configuration access address phase, the PCI address is divided into a number of fields
to determine the actual configuration register access. These fields, in combination with
the byte enables during the data phase create the unique encoding necessary to access
the individual registers of the configuration address space:
•
P_AD[7:2] -
Register Number. Selects one of 64 DWORD registers in the ATU PCI
configuration address space.
•
P_C/BE[3:0]# -
Used in data phase. Selects which actual configuration register is
used within the DWORD address. Creates byte addressability of the register space.
•
P_AD[10:8]
- Function Number. Used to select which function of a multi-function
device is being accessed. The ATU is function 0 and therefore it only responds to
000
2
in this bit field and ignore all other bit combinations.
•
P_AD[27:24]
- Upper Register Number. In PCI-X Mode 2, Upper Register Number
and Lower Register Number combine to select one of 1024 DWORD registers in the
ATU PCI configuration address space.
Note:
In PCI-X Mode 2, the ATU does not support any extended capabilities list items starting
at offset 100H indicated by a Null Enhanced Capability Header at offset 100H (i.e.,
Enhanced Capability Header with a Capability ID of 0000H, a Capability Version of 0H,
and a Next Capability offset of 000H).