Vela CineCast 2000-0422, Installation And User Manual

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Chapter 2 — Overview and Operation 53
INQUIRY Command
Control
The control byte is the ending byte of all SCSI Command Descriptor Blocks and
has the following format:
NOTE: The control byte of each SCSI command must be zero. Linked commands are
not supported by the decoder.
INQUIRY Command
(OpCode 0x12, 6 bytes)
The
INQUIRY
command allows the initiator (host adapter) to determine the kind of
SCSI devices attached to its SCSI Bus. It causes a device that is attached to a
SCSI bus to return information about itself. Since the function of the SCSI decod-
er does not fit into any of the standard SCSI device types, a new device type has
been defined. The function of the MPEG decoder is similar to a Direct Access
Storage Device, e.g., a hard disk, but also has characteristics of a CD-ROM. The
MPEG decoder can be viewed as a write-only device.
The decoder can provide two categories of data in response to an
INQUIRY
com-
mand: Standard Inquiry Data and Vital Product Data. Standard Inquiry Data
contains basic data about the decoder, and Vital Product Data comprise several
pages of additional data. Each Vital Product Data page requires a separate
INQUIRY
command from the initiator.
7 6 5
Reserved Flag Link Vendor Specific
4 3 2 1 0
0
Bit
Byte
Table 2-2. Control Byte Format
Table 2-3. INQUIRY Command Descriptor Block