pi7c8154b Pericom Semiconductor Corporation, pi7c8154b Datasheet - Page 70

• Manufacturer Part Number: pi7c8154b
• Description: Asynchronous 2-port Pci Bridge
• Manufacturer: Pericom Semiconductor Corporation

06-0008
9.1
9.2
9.3
9.4
EEPROM is used to initialize a select number of registers. This is accomplished after P_RESET#
is deasserted, at which time the data from the EEPROM will be loaded. The EEPROM interface is
organized into a 16-bit base, and the bridge supplies a 7-bit EEPROM word address. The bridge
does not control the EEPROM address input. It can only access the EEPROM with address input
set to 0.
AUTO MODE EEPROM ACCESS
The bridge may access the EEPROM in a WORD format by utilizing the auto mode through a
hardware sequencer. The EEPROM start control, address, and read/write commands can be
accessed through the configuration register. Before each access, the software should check the
Start EEPROM bit before issuing the next start.
EEPROM MODE AT RESET
During a reset, the bridge will autoload information/data from the EEPROM if the automatic load
condition is met. The first offset in the EEPROM contains a signature. If the signature is
recognized, the autoload will initiate right after the reset.
During the autoload, the bridge will read sequential words from the EEPROM and write to the
appropriate registers. Before the bridge registers can be accessed through the host, the autoload
condition should be verified by reading bit[3] offset 54h (EEPROM Autoload Status). The host
access is allowed only after the status of this bit becomes '1' which signifies that the autoload
initialization sequence has completed successfully.
EEPROM DATA STRUCTURE
The bridge will access the EEPROM one WORD at a time. The bit order during the address phase
is reverse that of the data phase. The data order starts with the MSB to the LSB during the address
phase, but starts with the LSB to the MSB during the data phase.
EEPROM CONTENT
EEPROM BYTE
ADDRESS
00 – 01h
02h
03h
CONFIGURATION
OFFSET
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REGION ENABLE
DESCRIPTION
EEPROM SIGNATURE
Autoload will only proceed if it reads a value of 1516h on
the first word loaded.
Enables or disables certain regions of the PCI configuration
space from being loaded with contents in the EEPROM.
bit[0]: reserved
bit[4:1]: 0000 = stop autoload at offset 03h
bit[7:5]: reserved
ENABLE MISCELLANEOUS FUNCTIONS
0001 = stop autoload at offset 0Fh
0011 = stop autoload at offset 2Bh
other combinations are undefined
MARCH 2006 REVISION 1.12
ASYNCHRONOUS 2-PORT
PCI-to-PCI BRIDGE
PI7C8154B