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5-152 Maxtor Atlas 10K V
Table 5-213 WRITE BUFFER Command-Field Descriptions
Field Description
Mode
Five modes are supported by the drive; Combined Header and Data, Data Only, Download Microcode and
Save, and Write Data from Echo Buffer. The permissible values for Buffer ID, Buffer Offset are as fol-
lows:
0000b
Combined Header and Data – In this mode, the data to be transferred is preceded by a 4-byte header that
contains reserved bytes that must be set to 0. The resulting descriptor and data are fetched from the initiator
during the command's data-out buffer transfer and, after the descriptor has been validated, only the data is
written to the controller's memory.
Buffer ID must be 0
Buffer Offset must be 0
Parameter List Length must be set to between 0 and 516 (4 bytes of header and up to 512 bytes of data).
0010b
Data Only– In this mode, the data-out buffer transfer contains buffer data. Data is written to the drive's
buffer starting at the location specified by the Buffer ID and Buffer Offset.
Buffer ID. When non-zero, the value specifies a specific track line in the controller’s cache. If Buffer ID
of zero is specified, the buffer referenced is the same as if Buffer ID of one were specified.
Buffer Offset. When non-zero, the value can range from 0 to one less than the number of sectors/track
multiplied by 512. This value must be either a zero or a multiple of 512.
Parameter List Length. This value must be a multiple of 512. The maximum value for this field is one
more than the number of sectors/track times 512. The minimum value is 0.
0101b
Download Microcode and Save.
In this mode, a microcode image is transferred to the drive, and if valid,
is saved in the controller's non-volatile memory. This image must be transferred with all buffers of the
same size (the last buffer of the transfer cannot be of a different size) and the buffer size must be a multiple
of 512. Most images are multiples of 512 and 1K. In that case, it is safe to have 512 byte transfers or 1K
transfers. For example, if the image size is 369K, then 738 512-byte buffers can be transferred or 369 1K
byte buffers can be transferred. It is also possible to transfer the image in one large buffer.
The controller does a hard reset on command completion. In Download Microcode and Save mode, the
other Command Descriptor Blocks are supported as follows:
Buffer ID – Undefined and ignored.
Buffer Offset – The offset of the buffer being transferred. For example: for 512 byte transfers use 0, 512,
1024, 1536,.... For 1K byte transfers use 0, 1024, 2048, 3072...
Parameter List Length – Must be the size of the buffer being transferred.
7
(0111b)
Download Microcode and Save with Offset. This mode acts the same as mode 0101b but is restricted to
sending the bytes in sequential order.
1010b
Write Data from Echo Buffer
In this mode, the host transfers data and stores it in an echo buffer. The data will be preserved in the echo
buffer unless there is an intervening command.
Buffer ID Ignored.
Buffer Offset Ignored.