Seagate Fibre Channel Interface - Manual (Page 152)

138 Fibre Channel Interface Manual, Rev. D
Field definitions (listed alphabetically)
DF_CTL (Data Field Control)
00h
Indicates no optional Fibre Channel headers are used.
D_ID (Destination Identifier)
The address of the drive if transfer is data to the drive and the address of the initiator originating the command if the trans-
fer is from the drive.
F_CTL (Frame Control)
This field is determined by the direction of the transfer and whether or not the frame is the last frame of the sequence.
For transfers to the drive, the initiator sets the F_CTL to 000008h or 000000h for all frames except the last frame of the
sequence. These values indicate the frame is from for the originator of the exchange (command) and whether the parame-
ter field is the relative offset. For the last frame of the sequence, the initiator sets the F_CTL to 09000Xh. This indicates the
frame is the last frame of the sequence and sequence initiative is transferred so the drive may send an additional FCP
XFER RDY or FCP RSP. The X represents the lower four bits of the F_CTL.
For transfers to the initiator, the drive sets the F_CTL to 800008h for all frames but the last frame of the sequence. This
indicates the frame is from the responder of the exchange (command) and the parameter field is the relative offset. For the
last frame of the sequence, the drive sets the F_CTL to 88000Xh. This indicates the frame is the last frame of the
sequence. Sequence initiative is held for transfer of another sequence or the FCP RSP. The X has the same meaning as
defined above.
OX_ID (Originator Exchange Identifier)
The value assigned by the initiator in the FCP CMND.
R_CTL (Routing Control)
Set to Solicited Data for the FCP DATA frame.
RO (Relative Offset)
The RO is a byte count offset between the first byte of the transfer address identified in the command and the first byte of
data in the frame payload. The drive sends a continually increasing RO on data frames when sending data. The drive does
not require or check the RO field on frames it receives. The drive uses the SEQ_CNT field to verify frames are received in
order.
RX_ID (Responder Identifier)
Not used by the drive. The value of FFFFh indicates the RX_ID is not being used.
SEQ_CNT (Sequence Count)
Set to 0000h on the first frame transferred. The SEQ_CNT is required to continually increase through a sequence and
across sequence boundaries if additional sequences are required to complete the transfer. The drive requires all received
frames to be in sequential order. Frames originated by the drive are sent in sequential order.
Table 83: Frame Control bit descriptions
Bit Description
3 Set to one (1) to indicate the parameter field is the relative offset.
2 0 (Reserved)
1 - 0 Number of fill bytes in the last word of the frame. The drive requires all data frames for transfers
to and from the media to be integer multiples of four bytes, so the drive requires the fill byte count
to be 0. For transfers that do not require media operations (e.g., inquiry data, read, and write
buffer), the drive supports the fill byte count.
Table
number
82
82
82
82
82
82
82
82