Figure 4-3. Type 0 Configuration; Pci Devicec - Compaq Deskpro 4000N 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 Device Configuration Access
PCI Device
North Bridge (82C595)
PCI Connector
South Bridge (82C586)
Graphics Controller
Network Interface Controller
The function number (CF8h, bits <10..8>) is used to select a particular function within a
multifunction device as shown in Table 4-4.
4-6 Compaq Deskpro 4000N and 4000S Personal Computers
31 30 24 23
Bus
Reserved
Number
31
IDSEL (only one signal line asserted)
Table 4-3.
Device No.
(CF8h <15..11>)
0
2
7
15
16
First Edition - September 1997
16 15 11 10 8 7
Device Function
Number Number
11 10 8 7
Function
Number
IDSEL
Wired to:
AD11
AD13
AD31
AD26
AD27
2 1 0
Register
0 0
Index
2 1 0
Register
Index