82571EB/82572EI EEPROM Information Guide
2
1.2
EEPROM Device
The EEPROM interface supports Serial Peripheral Interface (SPI) mode 0 and expects the
EEPROM to be capable of 2 MHz operation.
The 82571EB/82572EI is compatible with many sizes of 4-wire serial EEPROM devices. If
flexibility mode functionality is desired (ASF, PT, SPT, or full BMC), up to a 256 Kb serial SPI can
be used.
Note:
Minimum EEPROM sizes: 16 Kb (no manageability image); 128 Kb (any manageability image).
Recommended EEPROM sizes are: 32 Kb (no manageability image); 256 Kb (any manageability
image.
The 82571EB/82572EI automatically determines the address size to be used with the SPI
EEPROM it is connected to and sets the
EEPROM Size
field of the EEPROM/Flash Control and
Data Register (EEC.EE_ADDR_SIZE; bit 10). Software uses this size to determine the EEPROM
access method. The exact size of the EEPROM is stored within one of the EEPROM words.
Note:
The different EEPROM sizes have two different numbers of address bits (8 bits or 16 bits). Thus
they must be accessed with a slightly different serial protocol. Software must be aware of this if it
accesses the EEPROM using direct access.
1.3
Software Accesses
The 82571EB/82572EI provides two different methods for software access to the EEPROM. It can
either use the built-in controller to read the EEPROM or access the EEPROM directly using the
EEPROM’s 4-wire interface.
Software can use the EEPROM Read register (EERD) to cause the 82571EB/82572EI to read a
word from the EEPROM that the software can then use. To do this, software writes the address to
read into the
Read Address
field (EERD.ADDR; bits 15:2) and simultaneously writes a 1b to the
Start Read
bit (EERD.START; bit 0). The 82571EB/82572EI then reads the word from the
EEPROM, sets the
Read Done
bit (EERD.DONE; bit 1), and puts the data in the
Read Data
field
(EERD.DATA; bits 31:16). Software can poll the EEPROM Read register until it sees the
Read
Done
bit set, then use the data from the
Read Data
field. Any words read this way are not written to
the 82571EB/82572EI’s internal registers.
Software can also directly access the EEPROM’s 4-wire interface through the EEPROM/Flash
Control register (EEC). It can use this for reads, writes, or other EEPROM operations.
To directly access the EEPROM, software should follow these steps:
1. Write a 1b to the
EEPROM Request
bit (EEC.EE_REQ; bit 6).
2. Read the
EEPROM Grant
bit (EEC.EE_GNT; bit 7) until it becomes 1b. It remains 0b as long
as the hardware is accessing the EEPROM.
3. Write or read the EEPROM using the direct access to the 4-wire interface as defined in the
EEPROM/Flash Control & Data register (EEC). The exact protocol used depends on the
EEPROM placed on the board and can be found in the appropriate datasheet.
4. Write a 0b to the
EEPROM Request
bit (EEC.EE_REQ; bit 6).
