Figure 4-3. Type 0 Configuration - Compaq EN Series Technical Reference Manual

Chapter 4 System Support
Figure 4-3 shows 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.
Register 0CF8h
Results in:
AD31..0
w/Type 0
Config. Cycle
Figure 4–3. Type 0 Configuration Cycle
Type 0 configuration cycles are used for configuring devices on PCI bus # 0. Type 1
configuration cycles (reg. 0CF8h bits <1,0> = 01b) are passed on to PCI bus # 1 (if present).
Table 4-3 shows the standard configuration of device numbers and IDSEL connections for
components and slots residing on a PCI bus.
Table 4–3. PCI Device Configuration Access
PCI Component
82443 (North Bridge)
USB
82558 (NIC)
PCI Connector 1
PCI Connector 2
82371 (South Bridge)
NOTES
[1] CF8h bits <15..11>
The function number (CF8h, bits <10..8>) is used to select a particular function within a
multifunction device. Configurable functions present in system as shipped from the factory are
listed in Table 4-4.
4-6 Compaq Deskpro EN Series of Personal Computers
NetPC and Small Form Factor Models
31 30 24 23
Bus
Reserved
Number
31
IDSEL (only one signal line asserted)
Table 4-3.
PCI Component Configuration Access
Bus
0
0
0
0
0
0
First Edition - June 1998
16 15 11 10 8 7
Device Function
Number Number
11 10 8 7
Function
Number
Device
No. [1]
0
9
10
13
14
20
2 1 0
Register
0 0
Index
2 1 0
Register
Index
IDSEL
Wired to:
AD11
AD20
AD21
AD24
AD25
AD31