Register and Memory Mapping
6-2
Intel
82801BA ICH2 Datasheet
If a particular system platform does not want to support any one of Device 31’s Functions 1–6, they
can individually be disabled. The integrated LAN Controller will be disabled if no Platform LAN
Connect component is detected (See
Section 5.2, “LAN Controller (B1:D8:F0)” on page 5-5
).
When a function is disabled, it does not appear at all to the software. A disabled function will not
respond to any register reads or writes. This is intended to prevent software from thinking that a
function is present (and reporting it to the end-user).
NOTES:
1. The PCI to LPC bridge contains registers that control LPC, Power Management, System Management,
GPIO, processor interface, RTC, Interrupts, Timers, DMA.
6.2
PCI Configuration Map
Each PCI function on the ICH2 has a set of PCI configuration registers. The register address map
tables for these register sets are included at the beginning of the chapter for the particular function.
Configuration Space registers are accessed through configuration cycles on the PCI bus by the
Host bridge using configuration mechanism #1 detailed in the PCI 2.1 specification.
Some of the PCI registers contain reserved bits. Software must deal correctly with fields that are
reserved. On reads, software must use appropriate masks to extract the defined bits and not rely on
reserved bits being any particular value. On writes, software must ensure that the values of
reserved bit positions are preserved. That is, the values of reserved bit positions must first be read,
merged with the new values for other bit positions and then written back. Note the software does
not need to perform read, merge, write operation for the configuration address register.
In addition to reserved bits within a register, the configuration space contains reserved locations.
Software should not write to reserved PCI configuration locations in the device-specific region
(above address offset 3Fh).
6.3
I/O Map
The I/O map is divided into Fixed and Variable address ranges. Fixed ranges cannot be moved. In
some cases they can be disabled. Variable ranges can be moved and can also be disabled.
Table 6-1. PCI Devices and Functions
Bus:Device:Function
Function Description
Bus 0:Device 30:Function 0
Hub Interface to PCI Bridge
Bus 0:Device 31:Function 0
PCI to LPC Bridge
1
Bus 0:Device 31:Function 1
IDE Controller
Bus 0:Device 31:Function 2
USB Controller #1
Bus 0:Device 31:Function 3
SMBus Controller
Bus 0:Device 31:Function 4
USB Controller #2
Bus 0:Device 31:Function 5
AC’97 Audio Controller
Bus 0:Device 31:Function 6
AC’97 Modem Controller
Bus 1:Device 8:Function 0
LAN Controller
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