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Curtis Stevens wrote:
IDENTIFY DEVICE word 255 is marked mandatory in the table, but in the
description the word is clearly stated to be optional.
It should be mandatory.
Word 255 is divided
into 2 parts: Signature and Checksum. If the Signature (A5h) is present
then the checksum is valid.
Correct... And the way I seen it implemented on all drives to date.
In ATA8-ACS, the tables take precedence over the text. That would mean that
this field is mandatory. However, since the signature could be something
other than A5h, the checksum is optional. These conflicting statements are
very confusing and make the text appear to conflict with the table.
Back in the old days word 255 was most likely always 0000H so if it
is not 0000H then it should either be a valid signature and checksum
value -or- it indicates corrupted ID data (host take appropriate action).
Hale
--
++ Hale Landis ++ www.ata-atapi.com ++
