Datasheet

12.12 Metadata Storage Function

Metadata storage is a small, nonvolatile user area which address space is logically separated from the

main storage. The host can use metadata storage to store information on the data contents itself—for

example, available free blocks, device properties, or any summary information. The first implementation

of metadata storage in the drive provides just 32 bytes, however, the command set design does not pre-

clude any future enhancement.

The metadata concept itself is not bound to any specific physical medium, although the drive's metadata

storage has one important property for rotating devices: the host can access metadata without rotating

the disk. This medium property is expected to supplement the applicability of the drive for digital appli-

ances.

12.12.1 Metadata Storage Command Set

All metadata commands use command code B8h. Each command is specified as a subcommand of com-

mand B8h with Features Register containing the subcommand code. Cylinder Low and High registers are

used to specify metadata block address into 512-byte units which ranges from 0 to [metadata capacity in

bytes + 2] / 512. The drive provides 32 bytes of metadata capacity and the valid address for the drive is

0000h only. The Sector Count Register is used to specify the number of blocks transferred between the

host and the device. The Sector Number Register is reserved and must be 00h for future use.

Inquiry Metadata Media, which uses subcommand code 02h, returns 1 sector of data containing infor-

mation on the device's metadata storage. Read Metadata, which uses subcommand code 03h, can read

metadata contents. Inquiry Metadata Media and Read Metadata return a status word that indicates

whether the main storage contents have been modified since the last Write Metadata. The host can use

the status word to check if metadata is not consistent with the main storage contents. Write Metadata,

which uses subcommand code 04h, can write metadata. The device does not interpret metadata itself,

though it is recommended that the first 10 bytes of metadata be a unique number that signifies the iden-

tity of the remaining data.

In addition to define new command set, Identify Device is enhanced to use word 161 as a capability bit-

strap for CF command set extensions [which indicates support for the metadata command set].

Details of the command description are located in Section 13.5, "CF-ATA Command Description” on

page 85.

Hard disk drive specification for DSCM-11000/-10512/-10340