Intel PCI-X User Manual

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This register is used by software to cause the Ethernet controller to read individual words in the 
EEPROM. To read a word, software writes the address to the Read Address field and simulta-

neously writes a 1b to the Start Read field. The Ethernet controller reads the word from the 
EEPROM and places it in the Read Data field, setting the Read Done filed to 1b. Software can poll 

this register, looking for a 1b in the Read Done filed, and then using the value in the Read Data 

field. 

When this register is used to read a word from the EEPROM, that word is not written to any of 
Ethernet controller’s internal registers even if it is normally a hardware accessed word.

If software has requested direct pin control of the EEPROM using the EEC register, an access 

through the EERD register mechanism can stall until the EEC control has been released. Software 

should ensure that EEC.EE_REQ = 0b and that EEC.EE_GNT = 0b as well before attempting to 
use EERD to access the EEPROM.

Data

Address

DONE

START

START

0

0b

Start Read
Writing a 1b to this bit causes the EEPROM to read a (16-bit) word at 
the address stored in the EE_ADDR field and then storing the result in 
the EE_DATA field. This bit is self-clearing.

DONE

1

0b

Read Done
Set to 1b when the EEPROM read completes.
Set to 0b when the EEPROM read is in progress.
Writes by software are ignored.

ADDR

15:2

X

Read Address
This field is written by software along with Start Read to indicate the 
word to read.

DATA

31:16

X

Read Data. Data returned from the EEPROM read.