Seagate Fibre Channel Interface - Manual (Page 38)

24 Fibre Channel Interface Manual, Rev. D
All frames also have a header and a Cyclic Redundancy Check (CRC) field. The payload data field is optional
(but normally present) with the size and contents determined by the type of frame.
Figure 8. Frame structure
6.1.1.1 Start-of-frame (SOF) delimiter
Start-of-frame (SOF) delimiters signal the beginning of a frame. See “Frame delimiters” on page 17. This refer-
enced page contains a list of the various types of SOF delimiters.
6.1.1.2 Frame header
The frame header is 24 bytes long and is present in all frames. It is used to control link operation, control
device protocol transfers, and to detect missing frames or frames that are out of order.
Field definitions (listed alphabetically)
DF_CTL (Data Field Control)
Specifies the presence of optional headers in the payload of the frame. The drive does not support optional headers.
00h
The drive sets this field to 00h for all frames it originates (sends), and should also be 00h for all frames sent to the
drive.
D_ID (Destination Identifier)
The 3-byte N_Port address to which the frame is being sent.
Table 8: Frame header format
Byte
Word 0
(bits 31 - 24)
1
(bits 23 - 16)
2
(bits 15 - 08)
3
(bits 07 - 00)
0 R_CTL D_ID
1 Reserved S_ID
2 Type F_CTL
3 SEQ_ID DF_CTL SEQ_CNT
4 OX_ID RX_ID
5
Offset
Bytes
Transmission
Words
4 24 0 to 2112 4 4 24
SOF
Fill
Words
Fill
Words
Frame Header Payload Data Field CRC Fill Bytes EOF
1 6 0 to 528 1 1 6
Table
number
8
8