Figure 4-2. Configurationc - HP Deskpro EX Technical Reference Manual

Chapter 4 System Support
Two types of configuration cycles are used. A Type 0 (zero) cycle is targeted to a device on the
PCI bus on which the cycle is running. A Type 1 cycle is targeted to a device on a downstream PCI
bus as identified by bus number bits <23..16>. With three or more PCI buses, a PCI bridge may
convert a Type 1 to a Type 0 if it's destined for a device being serviced by that bridge or it may
forward the Type 1 cycle unmodified if it is destined for a device being serviced by a downstream
bridge. Figure 4-2 shows the configuration cycle format and how the loading of 0CF8h results in a
Type 0 configuration cycle on the PCI bus. The Device Number (bits <15..11> determines which
one of the AD31..11 lines is to be asserted high for the IDSEL signal, which acts as a "chip select"
function for the PCI device to be configured. The function number (CF8h, bits <10..8>) is used to
select a particular function within a PCI component.
Register 0CF8h
Results in:
AD31..0
(w/Type 00
Config. Cycle)
NOTES:
[1] Bits <1,0> : 00 = Type 0 Cycle, 01 = Type 1 cycle
Type 01 cycle only. Reserved on Type 00 cycle.
Figure 4-2. Configuration Cycle
Table 4-1 shows the standard configuration of device numbers and IDSEL connections for
components and slots residing on a PCI bus.
Table 4-1. PCI Device Configuration Access
PCI Component
82815 GMCH:
Memory Controller
AGP Bridge
i740 Graphics Controller
AGP slot
82801AA ICH:
PCI Bridge
LPC Bridge
EIDE Controller
USB I/F
SMBus Controller
Reserved
AC97 Audio Controller
AC97 Modem Controller
PCI Connector 1 (slot 1)
PCI Connector 2 (slot 2)
PCI Connector 3 (slot 3)
NOTES:
[1] Bus number in standard configuration. Can shift up if an AGP device with an additional
PCI bridge is installed in the AGP slot.
Not used.
4-4 Compaq Deskpro EX Series of Personal Computers
31 24 23
Bus
Reserved
Number
IDSEL (only one signal line asserted)
Table 4-1.
PCI Component Configuration Access
Function #
0
0
0
0
0
0
1
2
3
4
5
6
0
0
0
First Edition - August 2000
16 15 11 10 8 7
Device Function
Number Number
Function
Number
PCI
Device # Bus #
0 (00h) 0
1(01h) 0
2 (02h) 0
0 (00h) 1
30 (1Eh) 0
31 (1Fh) 0
31 (1Fh) 0
31 (1Fh) 0
31 (1Fh) 0
31 (1Fh) 0
31 (1Fh) 0
31 (1Fh) 0
8 (08h) 2 [1]
9 (09h) 2 [1]
10 (0Ah) 2 [1]
2 1 0 [1]
Register
Index
Register
Index
IDSEL
Wired
to:
--
--
--
AD24
AD25
AD26