Technical information

7-5
Register Descriptions
PCI Registers
PCI Configuration Header Registers
At the deassertion edge of the PCI reset, the AIC-6915 starts reading the serial EPROM. At
the same time, the
BR_A1
input is sampled. If the board has a pull-up on this pin, the
AIC-6915 replaces the default value of the following PCI configuration header registers:
Vendor ID, Device ID, SubClass, Base Class, SubSystem Vendor ID, SubSystem Device ID,
MinGnt (MinimumGrant), MaxLat (MaximumLatency) and Interrupt Pin, with the value
read from the serial EEPROM. The CCIS (Configuration Card Information Structure) and
MAC address are always read and stored in the appropriate registers. There are no default
values for these registers.
PCI VendorID Register
Type: R
Internal Registers Subgroup: PCI Configuration Header
Byte Address: 00h - 01h
PCI DeviceID Register
Type: R
Internal Registers Subgroup: PCI Configuration Header
Byte Address: 02h-03h
Table 7-3. PCI Vendor ID Register
Bit(s) rw
Reset
Value Description/Function
15:0 r 9004h
VendorID[15:0]:
The PCI Vendor Identifier register contains
product information used by the HOST. The Adaptec Vendor ID
default value is 9004h. This value can be changed to a value read
from an external serial EEPROM if
BR_A1
’ pin is ‘1’ when
PCIRST_
is deasserted.
Table 7-4. PCI Device ID Register
Bit(s) rw
Reset
Value Description/Function
15:0 r 6915h
DeviceID[15:0]:
The PCI Device Identifier registers contain
product information for use by the HOST during system
initialization and configuration. The two Device ID bytes contain
an Adaptec product code. The default product code for the
AIC-6915 is 6915h. This value can be changed to a value read from
an external serial EEPROM if
BR_A1
’ pin is ‘1’ when
PCI_PCIRST_
is deasserted.