Hitachi Ultrastar 15K450 (FC-AL) Hard Disk Drive Specification
87
Capability Entry(s) are used to specify standards and profiles, with which a node is compliant or supports. Nodes may also use
capability entries to exchange vendor unique parameters or information.
Table 65:RNC Capability Entry
The Flags field is as follows:
• Bit 7 – Invalidate Previous
This flag is only meaningful when the RNC Flags Select bit is set to one. Furthermore, it may only be set in the first
Capability Entry in the RNC Payload. When the RNC Flags Select field and the Invalidate Previous field are both set
to one, then the node issuing the RNC is requesting that the responding node invalidate this Capability Entry. All
bytes of the Capability Entry marked with the Invalidate flag must match the values set in a prior RNC exchange.
When the Invalidate Previous field is reset(0), the responding node selects one Capability Entry to return in the
RNC_ACC.
Since the drive does not support the Select Flag (it must be set to 0), the Invalidate Previous Flag has no meaning and
is ignored.
• Bit 6 – Extended
When this flag is set to zero, the Capability Entry shall be exactly 4 bytes long. If this flag is set to one, the length of
the Capability Entry is 4 bytes plus the length of the Extension.
• Bits 5-4 – Vendor Unique
• 0 0 Specifies that the Document Identifier field should be interpreted according to Table 66.
• 0 1 Specifies a Vendor Unique Document Identifier.
• 1 0 Specifies a Vendor Unique Document Identifier as defined by the vendor of the N_Port receiving
the RNC payload.
• 1 1 Reserved
• Bits 3-2 – Reserved
• Bits 1-0 - Preference
Preference is a two bit value that indicates the level of support or performance relative to the other capabilities sup-
ported by the node. It is used to aid a node in selecting a specific capability when multiple capabilities are supported.
The Preference field has a range from 0 to 3.
• 0 0 Best
• 0 1
Byte Item Size (Bytes)
0 Flags 1
1Document Identifier 1
2Low Revision 1
3High Revision 1
4-5 Reserved 0 or 2
6-7 Extension Length 0 or 2
8-> Extension 0 or n