AMD-761 datasheet(38/264 Pages) AMD

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AMD-761™ System Controller Programmer’s Interface

Chapter 2

AMD-761™ System Controller Software/BIOS Design Guide

24081D—February 2002

Preliminary Information

2.4.2

Configuration Register Access

The AMD-761 system controller implements most registers as

PCI configuration registers. The x86 software executes IN and

OUT instructions to I/O addresses of 0CF8 and 0CFC to access

all configuration registers. These are translated by the

AMD Athlon™ processor into AMD Athlon processor system bus

RdBytes and WrBytes commands with the lower 24 bits of the

address field containing the logical contents of the ConfigAddr

in “I/O:0CF8” on page 21 and “I/O:0CF8” on page 23.

Configuration accesses in the AMD-761 system controller

conform to the following rules:

The AMD-761 system controller is defined to be function 0

and 1, device 0; and function 0, device 1. The IDSEL pin of

all external PCI devices must be wired to 1 of AD[31:13] as

logically [12:11] are assigned to device 0, 1 (AMD-761

system controller).

Function 1, device 0 configuration space contains only the

DDR Programmable Delay Line (PDL) registers. This space

is enabled only when the appropriate bit is set in the PCI

Control register (see “Dev0:F0:0x4C” on page 47). Accesses

to the normal reserved PCI space of function 1 yields all 1s.

Accesses to function 1 are ignored when function 1 is not

enabled.

Device 0 accesses correspond to the host to PCI bridge

registers defined in Section 2.4.3 on page 27.

Device 1 accesses correspond to the PCI-to-PCI bridge

registers defined in Section 2.4.5 on page 117.

Access can be byte, word or DWord in length and must be

naturally aligned.

Northbridges are required to create type 0 and type 1 accesses

as follows:

If SysAdd[23:16] = 0 (Bus# = 2'h00), a type 0 config cycle is

generated and PCI AD[1:0] = 2'b00. Device#, SysAdd[15:11]

is decoded and asserted on PCI AD[31:11] for IDSEL.

If SysAdd[23:16] != 0 (Bus# != 2'h00), a type 1 config cycle is

generated and PCI AD[1:0] = 2'b01. Bus# and Device# fields

are passed onto the PCI directly with no decoding. PCI

AD[31:24] = 2'h00.

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