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204 Software Developer’s Manual
Dual Port Characteristics
Many of the fields of the PCI header space contain hardware default values that are either fixed or
can be overridden using EEPROM, but cannot be independently specified for each logical LAN
device. The following fields are considered to be common to both LAN devices:
24h Base Address 5
28h Cardbus CIS Pointer (not used)
2Ch Subsystem ID Subsystem Vendor ID
30h Expansion ROM Base Address
34h Reserved Cap_Ptr
38h Reserved
3Ch Max_Latency 00h
Min_Grant
FFh
Interrupt Pin
01h or 00h)
Interrupt Line
00h
Vendor ID
The Vendor ID of the Ethernet controller can be specified via EEPROM, but
only a single value can be specified. The value is reflected identically for both
LAN devices.
Revision
The revision number of the Ethernet controller is reflected identically for both
LAN devices.
Header Type
This field indicates if a device is single function or multifunction. The value
reflected in this field is reflected identically for both LAN devices, but the actual
value reflected depends on LAN Disable configuration.
When both Ethernet controller LAN ports are enabled, both PCI headers return
80h in this field, acknowledging being part of a multi-function device. LAN A
exists as device “function 0”, while LAN B exists as device “function 1”.
If one of the LAN ports is disabled, then only a single-function device is
indicated (this field returns a value of 00h), and the LAN exists as device
“function 0”.
Subsystem ID
The Subsystem ID of the Ethernet controller can be specified via EEPROM,
but only a single value can be specified. The value is reflected identically for
both LAN devices.
Subsystem Vendor ID
The Subsystem Vendor ID of the Ethernet controller can be specified via
EEPROM, but only a single value can be specified. The value is reflected
identically for both LAN devices.
Class Code,
Cap_Ptr,
Max Latency,
Min Grant
These fields reflect fixed values that are constant values reflected for both LAN
devices.
Byte Offset Byte 0 Byte 1 Byte 2 Byte 3