Datasheet

4–3
Table 4–1. Quadlet-Transmit Format
FIELD NAME DESCRIPTION
spd The spd field indicates the speed at which the current packet is to be sent (00 = 100 Mbits/s,
01 = 200 Mbits/s, and 10 = 400 Mbits/s, and 11 is undefined).
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 is 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 IEEE
1394
-1995 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 1394-1995 standard).
destinationID The destinationID field is the concatenation of the 10-bit bus number and the 6–bit node num-
ber that forms the destination node address of the current packet.
rCode
Specifies the result of the read request transaction. The response codes that may be returned
to the requesting agent are defined as follows:
Response
Code
Name Description
0 resp_complete Node successfully completed requested operation.
1–3 Reserved
4 resp_conflict_error Resource conflict detected by responding agent.
Request may be retried.
5 resp_data_error Hardware error. Data not available.
6 resp_type_error Field within request packet header contains
unsupported or invalid value.
7 resp_address_error Address location within specified node not accessible.
8 – Fh Reserved
destination OffsetHigh,
destination OffsetLow
The concatenation of these two fields addresses a quadlet in the destination node address
space. This address must be quadlet aligned (modulo 4).
quadlet data For write requests and read responses, the quadlet data field holds the data to be transferred.
For write responses and read requests, this field is not used and should not be written into the
FIFO.
4.1.2 Block Transmit
The IEEE 1394–1995 standard specified four types of block transmit packets: write request, write response,
read request, and read response packet. Table 4–2 describes the details of each packet.
4.1.2.1 Block Write-Request and Read-Request packets
The format for a block write-request packet is shown in Figure 4–5. The first quadlet contains the packet
control information. The second and third quadlets contain the 64-bit, quadlet-aligned address. The first 16
bits of the fourth quadlet contains the dataLength field. This is the number of bytes of data in the packet.
The remaining 16 bits represent the extended_tCode field (see Table 6–11 of the IEEE 1394-1995 standard
for more information on extended_tCodes). The block data, if any, follows the extended_tCode. The format
for a block read-request is shown in Figure 4–6.