FC-4 (FCP) Features
74 SL500: Interface Reference Manual • July 2008 Revision: F • 96122
If the FCP_RESID_UNDER bit is set to 1b, a transfer that did not fill the buffer to
the expected displacement. Failure to transfer FCP_DL bytes does not
necessarily indicate an error for some devices and commands.
■ If the FCP_RESID_OVER bit is set, the transfer was truncated because the data
transfer required by the SCSI command extended beyond the displacement
value of FCP_DL. Those bytes that could be transferred without violating the
FCP_DL value may or may not have been transferred.
■ Commands that do not contain an FCP_DATA IUs, FCP_RESID_UNDER and
FCP_RESID_OVER are set to 0b, and the value of the FCP_RESID is undefined.
Response Payload
TABLE 5-22 lists the FCP_RSP payload fields:
Response Codes
The Response Code field (FCP_RSP_INFO) contains information that describes the
failures detected during the execution of an I/O operation and conforms to the
following rules:
■ The FCP_RSP_INFO does not contain link error information because FC-PH
provides the mechanisms for presenting these errors.
■ The FCP_RSP_INFO does not contain SCSI logical unit error information
because that information is in the FCP_STATUS and FCP_SNS_INFO fields.
■ RSP_CODE values of 04h and 05h are not valid responses to SCSI commands.
The RSP_CODE is independent of the SCSI Status and should be examined
before interpretation of the SCSI Status.
■ For other non-zero values of the RSP_CODE, the SCSI Status may not be valid.
TABLE 5-22 FCP_RSP Payload
Feature
FC-Tape
StorageTekInitiator Target
FCP_CONF_REQ A R Y
FCP_SNS_INFO R I Y
FCP_SNS_LEN (total) R
≤ 128 20
FCP_SNS_LEN_VALID R I Y
Length of Additional Sense Bytes in FCP_SNS_INFO R
≤ 120 16
FCP_RSP_INFO R I Y
FCP_RSP_LEN R 0 or 8 8
FCP_RSP_LEN_VALID R I Y
FCP_RESID R R Y
FCP_RESID_OVER R I Y
FCP_RESID_UNDER R I Y
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