SCSI Description
5-108 Maxtor Atlas 10K III
The READ BUFFER command is used in c onj unct ion with th e WRITE BUFFER
command. It allows the initiator to gain access to the data storage areas within the
drive's cont roller. In particular, t hese two comman ds are used to chec k the integrity
of the buff er-initiat or data path, indepen dent of the media, typic ally for faul t isolat ion
in the event of a f ailure. In addi tion, these commands can be used to verify the caching
policies of the drive controller or other kinds of diagnostic and verification work.
Both the READ BUFFER and the WRITE BUFFER commands have a buffer ID
and a buffer offset data field defined in their Control Descriptor Block. In the
C omb ined He ad e r and D a ta Mo d e , if both are s et to 0, refere n ce i s m ad e to a single
512-byte buffer set aside in the drive controller's data memory (independent of cache).
Th i s al l o ws a n i nitia to r to v e ri fy th e da ta p a th fro m the contro l l e r's d ata m e mo ry to
the initiator without affecting the drive's internal data caches. The data format and field
descriptions are shown in Table 5-129 and Table 5-130 respectively.
READ BUFFER Command-Data Format
0 Operati on Code (3Ch)
1 Reserved Mode
2Buffer ID
3 - 5 Buffer Offset
6 - 8 Allocation Length
9 Control