SCS I Description
M axtor Atlas 10K III 5-109
READ BUFFER Command-Field Descriptions
Mode Four modes are supported by the drive; Combined Header and Data, Data Only, Descrip-
tor Onl y, and Read Dat a fr om Echo Buffer. The perm issible value s for Buff er ID, Buffer
Offset, are as fol lows:
0000b
Combined Header and Data – In this mode, data to be transferred is preceded by a 4-
byte header that contains the buffer capacity. The resulting descriptor and data are trans-
ferred to the initiator during the command’s data-in buffer t ransfer .
must be 0
must be 0
Allocation length must be set to bet w een 0 and 516 (4 byt es of header and up to 512
bytes of data).
0010b
Data Only– In this m ode, the dat a-in bu ffer transfer contain s data from t he controller’s
memory.
. When non-zero, the val ue specif ies a specific track line in the control ler’s
cache. If Buff er ID of zero i s specif ied, the buffer r efe renced is t he same as i f a Buffe r ID
of one were specified.
. When non-zero, the value of Buffer Offset can range from 0 to one less
than the number of sect ors/track m ulti pli ed by 512. Thi s value must be either a zero or
a mu ltiple of 512.
Must be between zero and the maximum number of sectors/track mul-
tipl ied by 5 12.
0011b
Descri ptor Only
When requesting a descriptor (a description of the buffer referenced in the Buffer IDfield),
the resulting dat a is the offset boundary requirements and the l ength o f each buffer.
When non-z ero, the val ue specif ies a specif ic track li ne within th e control ler’s
cache. If Buffer ID of 0 is specified, the buffer referenced is the same as if a Buffer ID of
1 were sp ecified.
Must be zero
Must be between 4 (header) a nd the maxim um number of sectors/
track mul tiplied by 512 + header size.
1010b Read Data fr om Ech o Buffer
In this mode, the drive transfers data to the host from the echo buffer. The echo buffer
will transfer the same data as when t he W R ITE BUFFER command wi th the mode field
se t to ec ho buffer was is su ed .
Ignored.
Ignored.