Subsystem Vendor Id; Eeprom Upload At Pci Reset; Register Load From Bios; Table 3-7. Eeprom Upload Sequence - Conexant Fusion 878A Manual

3.0 Electrical Interfaces
3.5 I2C Serial EEPROM Interface

3.5.2 Subsystem Vendor ID

3.5.2.1 EEPROM Upload
at PCI Reset

Table 3-7. EEPROM Upload Sequence

Master
Control Data
START 0xA0
0xFC
START 0xA1
— —
— —
— —
— —
3.5.2.2 Register Load
from BIOS
3-24
PCI Configuration Header Location 0x2C specifies the subsystem vendor ID and
the subsystem ID. If an external EEPROM is present, the subsystem vendor ID
and subsystem ID and vital product data are uploaded. If an external EEPROM is
not present, the 32 bits of the header register default to 0x0000, and the register
can be programmed using BIOS.
This chapter defines the subsystem vendor ID configuration with and without
an EEPROM present. For more details on the Function 1 definition, refer to
Section 6.1. The Function 0 subsystem vendor ID registers are defined starting on
0x00—Vendor and Device ID
registers are defined starting on
The 32-bit subsystem IDs are read from the EEPROM by taking control of the
2
I C circuit just after PCI reset and performing a 4-byte sequential read access
transaction in the 100 kHz mode, starting at physical address 0xFC. The full read
sequence is detailed in Table
Slave
Data Control
— ACK
— ACK
— ACK
0x —
0x —
0x —
0x —
If at any time the slave device issues a NACK (because the device is not
present), the sequence is aborted, and the subsystem vendor IDs read
0x00000000. Normally it will take ~660 µs to read this DWORD into the PCI
configuration register. If this register is accessed before it is updated, the PCI
target will issue a RETRY.
The Subsystem IDs register is read-only. However, by enabling SVIDS_EN in the
user-defined PCI configuration control register, the Subsystem Vendor IDs can be
written. Then SVIDS_EN should be disabled. This value needs to be programmed
before OS boots and has access during configuration. This must occur via support
from the BIOS versus the IC driver. If this feature can be supported by software
(and Vital Product Data is not supported), then the external EEPROM is not
required.
Conexant
Register, and the Function 1 subsystem vendor ID
0x00—Vendor and Device ID
3-7.
Master
Control
— Write control byte with slave chip address
— Data bytes base address
— Read control byte with slave chip address
ACK Subsystem ID [15:8] at 0xFC
ACK Subsystem ID [7:0] at 0xFD
ACK Subsystem Vendor ID [15:8] at 0xFE
NACK,STOP Subsystem Vendor ID [7:0] at 0xFF
Fusion 878A
PCI Video Decoder
Register.
Comment
100600B