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

SCSI Description
T a b l e 5 - 2 1 9 WRITE BUFFER Command-Field Descriptions
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Four modes are supported by the drive; Combined Header and Data, Data Only, Download
Mode Microcode and Save, and Write Data from Echo Buffer. The permissible values for Buffer
ID, Buffer Offset are as follows:
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.
0000b must be 0
$ W H H G T + &
$ W H H G T 1 H H U G V
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bytes of data).
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.
. When non-zero, the value specifies a specific track line in the controller's cache.
$ W H H G T + &
If Buffer ID of zero is specified, the buffer referenced is the same as if Buffer ID of one were
specified.
0010b
$ W H H G T 1 H H U G V
sectors/track multiplied by 512. This value must be either a zero or a multiple of 512.
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field is one more than the number of sectors/track times 512. The minimum value is 0.
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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
0101b
The controller does a hard reset on command completion. In Download Microcode and Save
mode, the other Command Descriptor Blocks are supported as follows:
– Undefined and ignored.
$ W H H G T + &
$ W H H G T 1 H H U G V
fers use 0, 512, 1024, 1536,.... For 1K byte transfers use 0, 1024, 2048, 3072...
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(0111b) is restricted to sending the bytes in sequential order.
Write Data from Echo Buffer
In this mode, the host transfers data and stores it in an echo buffer. The data will be pre-
served in the echo buffer unless there is an intervening command.
1010b
Ignored.
$ W H H G T + &
$ W H H G T 1 H H U G V
5-174 Maxtor Atlas 10K III
must be 0
must be set to between 0 and 516 (4 bytes of header and up to 512
. When non-zero, the value can range from 0 to one less than the number of
. This value must be a multiple of 512. The maximum value for this
In this mode, a microcode image is transferred to the drive,
– The offset of the buffer being transferred. For example: for 512 byte trans-
– Must be the size of the buffer being transferred.
Ignored.
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This mode acts the same as mode 0101b but
buffer.