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82571EB/82572EI EEPROM Information Guide
Variable length fields are used to limit the total amount of EEPROM that is used for iSCSI boot
information. Each field is preceded by a single byte that indicates how much space is available for
that field. For example; if the Initiator Name field is being limited to 128 bytes, then it is preceded
with a single byte with the value 128. The following field begins 128 bytes after the beginning of
the Initiator Name field regardless of the actual size of the field. The variable length fields must be
null terminated unless they reach the maximum size specified in the length byte.
1.10
Checksum Word Calculation (Word 3Fh)
The Checksum word (3Fh) should be calculated such that after adding all the words (00h-3Fh),
including the Checksum word itself, the sum should be BABAh. The initial value in the 16-bit
summing register should be 0000h and the carry bit should be ignored after each addition. This
checksum is not accessed by the Ethernet controller. If CRC checking is required, it must be
performed by software.
Note: Hardware does not calculate checksum word 3Fh during EEPROM write; it must be calculated by
software independently and included in the EEPROM write data. Hardware does not compute a
checksum over words 00h-0Fh during EEPROM reads in order to determine the validity of the
EEPROM image; this field is provided strictly for software verification of EEPROM validity. All
hardware configuration based on word 00h-0Fh content is based on the validity of the Signature
field of EEPROM Initialization Control Word 1. Signature must be 01b.
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