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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
Bit Definitions
AGP/PCI Status, I/O Base and Limit (Dev1:0x1C)
Bit
Name
Function
31
PERR_Rcv
Detected Parity Error
This bit is always Low because the AMD-761™ system controller does not support
parity checking.
30
SERR_Rcv
Signaled System Error
This bit is set whenever the AMD-761 system controller received AGP SERR#. This bit is
cleared by writing a 1. Refer to Table 7 on page 34 for details about SERR# assertion
and status.
29
Mas_ABRT
Received Master Abort
This bit is set by the AMD-761 system controller whenever a bus master transaction
(except for a special cycle) is terminated due to a master abort. This bit is cleared by
writing a 1.
28
Trgt_ABRT
Receive Target Abort
This bit is set by the AMD-761 system controller whenever a bus master transaction (except
for a special cycle) is terminated due to a target abort. This bit is cleared by writing a 1.
27
Trgt_ABRTS
_Signaled
Signaled Target Abort
This bit is always 0 because the AMD-761 system controller does not terminate
transactions with target aborts.
26–25
DEVSEL_Timing
DEVSEL# Timing
This field is always 0x1, indicating that the AMD-761 system controller supports medium
DEVSEL# timing.
24
Data_PERR
Data PERR#
This bit is always 0 because the AMD-761 system controller does not report data
parity errors.
23
Fast_B2B
Fast Back-to-Back Capable
This bit is always 0, indicating that the AMD-761 system controller as a target is not
capable of accepting fast back-to-back transactions when the transactions are not to the
same agent.
22
UDF
User-Definable Features
This bit is always 0, indicating that UDF is not supported on the AMD-761 system
controller.
21
66M
66-MHz Capable
This bit is always 1, indicating that the AMD-761 system controller supports 66 MHz on
device 1.
20
Cap_Lst
Capabilities List
This bit is always 0, indicating that the configuration space of this device does not support
a capabilities list.
19–16
Reserved
Reserved
15–12
IO_Lim[15:12]
I/O Limit (Write)
This bit field indicates the upper writable 4 bits that define the top address of an address
range that is used by the bridge to determine when to forward I/O transactions from one
interface to the other.
11–8
IO_Lim_R
I/O Limit (Read)
The lower read-only 4 bits define the top address of an address range that is used by the
bridge to determine when to forward I/O transactions from one interface to the other. 0x1
indicates that 32-bit I/O address decoding is available.