Seagate Fibre Channel Interface - Manual (Page 39)

Fibre Channel Interface Manual, Rev. D 25
F_CTL (Frame Control)
This 3-byte (24-bit) field contains control information relating to the frame content as defined below.
Offset
This 4-byte field is used in data frames to define the relative offset (displacement) of the first byte of the payload from the
base address of the command. When the relative offset is present, bit 3 of F_CTL is set to indicate that relative offset is
valid.
The drive uses the SEQ_CNT value to verify that frames are being received in order. The drive does not use relative offset
in frames it receives. The drive sends relative offset information in data frames it originates.
Table 9: Frame Control (F_CTL) bit definitions
Bit Definition Description
23
Exchange context 0 = Frame is from the exchange originator.
1 = Frame is from the exchange responder.
22
Sequence context 0 = Initiator
1 = Recipient
21
First sequence 0 = Not the first sequence of the exchange.
1 = First sequence of the exchange.
20
Last sequence 0 = Not the last sequence of the exchange.
1 = Last sequence of the exchange.
19
End of sequence 0 = Not the last frame of the sequence.
1 = Last frame of the sequence.
18
End connection Not supported.
17
Chained sequence Not supported.
16
Sequence initiative 0 = Hold sequence initiative.
1 = Transfer sequence initiative.
15
X_ID reassigned Not supported.
14
Invalid X_ID Not supported.
13
12
11
10
Reserved
9
Retransmitted
sequence Not supported.
8
Unidirectional
transmit
Not supported.
7
6
Continue sequence
condition Not supported.
5
4
Abort sequence
condition
Not supported.
3
Relative offset
present 0 = Parameter field not meaningful.
1 = Parameter field equals relative offset.
2
Reserved
1
0
Fill data bytes End of data field fill bytes
00 = 0 bytes of fill.
01 = 1 byte of fill (last byte of data field).
02 = 2 bytes of fill (last 2 bytes of data field).
03 = 3 bytes of fill (last 3 bytes of data field).
8
8