Read Buffer Command-Field Descriptions - Maxtor ATLAS 10K III Product Manual

T a b l e 5 - 1 3 0 READ BUFFER Command-Field Descriptions
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Four modes are supported by the drive; Combined Header and Data, Data Only, Descrip-
Mode tor Only, and Read Data from Echo Buffer. The permissible values for Buffer ID, Buffer
Offset, are as follows:
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 transfer.
0000b must be 0
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Allocation length must be set to between 0 and 516 (4 bytes of header and up to 512
bytes of data).
Data Only– In this mode, the data-in buffer transfer contains data from the controller's
memory.
. When non-zero, the value specifies a specific track line in the controller's
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cache. If Buffer ID of zero is specified, the buffer referenced is the same as if a Buffer ID
of one were specified.
0010b
. When non-zero, the value of Buffer Offset can range from 0 to one less
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than the number of sectors/track multiplied by 512. This value must be either a zero or
a multiple of 512.
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tiplied by 512.
Descriptor Only
When requesting a descriptor (a description of the buffer referenced in the Buffer IDfield),
the resulting data is the offset boundary requirements and the length of each buffer.
When non-zero, the value specifies a specific track line within the controller's
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0011b cache. If Buffer ID of 0 is specified, the buffer referenced is the same as if a Buffer ID of
1 were specified.
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track multiplied by 512 + header size.
1010b Read Data from Echo 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 the WRITE BUFFER command with the mode field
set to echo buffer was issued.
Ignored.
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must be 0
Must be between zero and the maximum number of sectors/track mul-
Must be zero
Must be between 4 (header) and the maximum number of sectors/
Ignored.
SCSI Description
Maxtor Atlas 10K III 5-109