82830MP Datasheet, PDF (38/159 Pages) Intel Corporation – Intel 830MP Chipset: 82830MP Graphics and Memory Controller Hub (GMCH-M)

Intel® 830MP Chipset
R
4.2.1 Intel 82830MP GMCH-M Configuration Cycle Flow Charts
Figure 3. Configuration Cycle Flow Chart
DW I/O Write to
CONFIG_ADDRESS
with bit 31=1
I/O Read/Write to
CONFIG_DATA
GMCH-M Generates
Type 0 Access to _Yes
AGP/PCI1
BUS#=0
No
Yes
DEV#=0,
FN#=0
BUS#=
SECONDARY BUS
in GMCH-M
Dev #1
No
No
DEV#=1,
FN#=0
GMCH-M Generates
Type 1 Access to _Yes
BUS# > SEC BUS
AGP/PCI1
BUS# <= SUB BUS
No
Yes
GMCH-M Claims Bus #0 /
Device #0 / Function #0
Yes
GMCH-M Claims Bus #0 /
Device #1 / Function #0
No
GMCH-M Generates
hub I/F Type 1
Configuration Cycle
GMCH-M Generates
hub I/F Type 0
Configuration Cycle
4.2.2
A detailed description of the mechanism for translating CPU I/O bus cycles to configuration cycles on
one of the two buses is described in Figure 3 above.
PCI Bus Configuration Mechanism
The PCI Bus defines a slot based "configuration space" that allows each device to contain up to 8
functions with each function containing up to 256, 8-bit configuration registers. The PCI specification
defines two bus cycles to access the PCI configuration space: Configuration Read and Configuration
Write. Memory and I/O spaces are supported directly by the CPU. Configuration space is supported by
a mapping mechanism implemented within the GMCH-M. The PCI specification defines two
mechanisms to access configuration space, Mechanism #1 and Mechanism #2. The GMCH-M supports
only Mechanism #1 for PCI configuration accesses.
The configuration access mechanism makes use of the CONFIG_ADDRESS Register and
CONFIG_DATA Register. To reference a configuration register, a Dword I/O write cycle is used to
place a value into CONFIG_ADDRESS that specifies the PCI bus, the device on that bus, the function
within the device, and a specific configuration register of the device function being accessed.
CONFIG_ADDRESS[31] must be 1 to enable a configuration cycle. CONFIG_DATA then becomes a
38
Datasheet
298338-001