7
–
6
The block-receive format through the FIFO is shown in Figure 7-7.
3
2
1
0
7
6
5
4
11
10
9
8
15
14
13
12
19
18
17
16
20 21
31
30
29
28
27
26
25
24
23
22
spd
numofQuadlets
sourceID
destinationOffsetHigh
0
0
0
0
0
ackCode
0
0
0
0
0
0
prioity
tCode
rt
tLabel
destinationID
destinationOffsetLow
dataLength
block data (if any)
extended_tCode
Figure 7
–
7. Data Mover Block-Receive Format
Table 7
–
4. Block-Receive Format Functions
FIELD NAME
DESCRIPTION
numofQuadlets
Total number of quadlets in the current packet (payload and header quadlets only)
ackCode
This 5-bit field holds the acknowledge code sent by the receiver for the current packet (see
Table 6-13 in the draft standard).
destinationID
The destinationID field is the concatenation of the 10-bit bus number and the 6-bit node
number that forms the node address to which the current packet is being sent.
tLabel
The tLabel field is the transaction label, which is a unique tag for each outstanding transaction
between two nodes. This field is used to pair up a response packet with its corresponding
request packet.
rt
The rt field contains the retry code for the current packet is 00 = new, 01 = retry_X, 10 = retryA,
and 11 = retryB.
tCode
The tCode field is the transaction code for the current packet (see Table 6-10 of the
IEEE-1394 standard).
priority
The priority field contains the priority level for the current packet. For cable implementation,
the value of the bits must be zero (for backplane implementation, see clause 5.4.1.3 and
5.4.2.1 of the IEEE-1394 standard).
sourceID
The sourceID field contains the node ID of the sender of the current packet.
destination OffsetHigh,
destination OffsetLow
The concatenation of the destination OffsetHigh and the destination OffsetLow fields
addresses a quadlet in the destination nodes address space. This address must be quadlet
aligned (modulo 4). The upper 4 bits of the destination OffsetHigh field are used as the
response code for lock-response packets and the remaining bits are reserved.
dataLength
For write request, read responses, and locks, the dataLength field indicates the number of
bytes being transferred. For read requests, the dataLength field indicates the number of
bytes of data to be read. A write-response packet does not use this field. Note that the number
of bytes does not include the head, only the bytes of block data.
extended_tCode
The extended_tCode field contains the block extended_tCode to be performed on the data in
the current packet (see Table 6-11 of the IEEE-1394 standard).
block data
The block data field contains any data being transferred for the current packet. Regardless of
the destination address or memory alignment, the first byte of the data appears in byte 0 of the
first quadlet of this field. The last quadlet of the field is padded with zeros out to four bytes, if
necessary.
spd
The spd field indicates the speed at which the current packet was sent. 00 = 100 Mb/s,
01 = 200 Mb/s, 10 = 400 Mb/s, and 11 is undefined for this implementation.