Write Buffer Command Descriptor Block-Data Format - Maxtor ATLAS 10K III Product Manual

The WRITE BUFFER and the READ BUFFER commands allow the initiator to
gain access to the data storage areas within the drive controller. These commands are
used to check the integrity of the buffer-initiator data path independent of the storage
medium, typically for fault isolation. The commands can be used to verify the caching
policies of the controller or other kinds of debug work. In addition, the WRITE
BUFFER command supports controller microcode downloads. The data format and
field descriptions are shown in Table 5-218 and Table 5-219 respectively.
Both the READ BUFFER and WRITE BUFFER commands have a Buffer ID and a
Buffer Offset data field defined in their Command Descriptor Block. In combined
Header and Data Mode, if both are set to 0, reference is made to a single, 512-byte
buffer set aside in the controller's data memory, independent of cache. This allows an
initiator to verify the data path from the controller's data memory to the initiator
without affecting the drive's internal data caches.
T a b l e 5 - 2 1 8 WRITE BUFFER Command Descriptor Block-Data Format
$ K V
 
$ [ V G
0
1
2
3 - 5
6 - 8
9
 
Operation Code (3Bh)
Reserved
Buffer ID
Buffer Offset
Parameter List Length
Control
SCSI Description
  
Mode
Maxtor Atlas 10K III

5-173