Maxtor 10K V manual Read Buffer Command 3Ch, 123READ Buffer Command-Data Format

5.20READ BUFFER Command (3Ch)

The READ BUFFER command is used in conjunction with the WRITE BUFFER command. It allows the initiator to gain access to the data storage areas within the drive's controller. In particular, these two commands are used to check the integrity of the buffer-initiator data path, independent of the media, typically for fault isolation in the event of a failure. In addition, 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 Combined Header and Data Mode, if both are set to 0, reference is made to a single 512-byte buffer set aside in the drive 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. The data format and field descriptions are shown in Table 5-123 and Table 5-124 respectively.

Table 5-123READ BUFFER Command-Data Format

Bit	7	6		5	4		3	2		1	0
Byte
0					Operation		Code (3Ch)
1			Reserved						Mode
2						Buffer ID
3 - 5					Buffer Offset
6 - 8					Allocation Length
9						Control

5-94 Maxtor Atlas 10K V