FCP Constructs
8946121402 3-3
The FCP_LUN value format is described in Table3-3 or the value is 0. The latter refers to the
SESD on the local switch. The FCP_CNTL value is set to 1, 2 or 0 depending on whether
READ DATA,WRITE DATA or neither is involved in the command. TheFCP_CDB value
contains the appropriate command descriptor. The FCP_DL field contains a count of the
maximum number of data bytes to be transferred to or from the target for the command.
FCP Transfer Ready Information Unit
The FCP_XFER_RDY Information Unit contains SCSI-3 data delivery service parameters
required by the initiator and must be transmitted preceding each read or write FCP_DATA IU.
Note: The SESD does not generate this optional Information Unit.
FCP Data Information Unit
The FCP_DATA Information Unit transfers the actual data.
FCP Response Information Unit
Table3-4 shows the FCP_RSP that carries the response status and sense information associated
with a particular FCP_CMND.
Table 3-3 FCP_CMND IU Format
Byte Size Field Name Byte Number Description
8 FCP_LUN 0 - 7 Logical Unit Number
4 FCP_CNTL 8 - 11 Control flags and bits for task/execution management
16 FCP_CDB 12 - 27 SCSI command descriptor block
4 FCP_DL 28 - 31 Data Length
Table 3-4 FCP_RSP Format
Byte Size Field Name Description
8 Reserved Reserved
4 FCP_STATUS Status of the (linked/previous) request
4 FCP_RESID Residual Count
4 FCP_SNS_LEN Length of Sense Information (FCP_SNS_INFO)
4 FCP_RSP_LEN Length of Response Information (FCP_RSP_INFO)
m FCP_RSP_INFO FCP Response Information
n FCP_SNS_INFO SCSI Sense Information