TSB12C01APZ datasheet(34/59 Pages) TI

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4–4

responses. For block read requests and block write responses, the data field is omitted. The last quadlet

contains packet-reception status.

1 2 3

5 6 7

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

spd

tLabel

tCode

priority

sourceID

destinationOffsetHigh

destinationOffsetLow

block data (if any)

ackSent

destinationID

dataLength

extended_tCode

Figure 4–4. Block-Receive Format

Table 4–4. Block-Receive Format Functions

FIELD NAME

DESCRIPTION

destinationID

This is the concatenation of the 10-bit bus number and the 6-bit node number that forms the

node address to which this packet is being sent.

tLabel

This field is the transaction label, which is a unique tag for each outstanding transaction

between two nodes. This is used to pair up a response packet with its corresponding request

packet.

The retry code for this packet is 00 = new, 01 = retry_X, 10 = retryA, and 11 = retryB.

tCode

tCode is the transaction code for this packet. (See Table 6–10 of the IEEE 1394-1995

standard).

priority

This field contains the priority level for this 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.

sourceID

This is the node ID of the sender of this packet.

destination OffsetHigh,

destination OffsetLow

The concatenation of these two fields addresses a quadlet in the destination node’s address

space. This address must be quadlet aligned (modulo 4). The upper four 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, this field indicates the number of bytes being

transferred. For read requests, this 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 block extended_tCode to be performed on the data in this packet. See Table 6–11 of the

IEEE 1394-1995 standard.

block data

This field contains any data being transferred for this 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 this field is padded with zeros out to four bytes, if necessary.

spd

This field indicates the speed at which this packet was sent. 00 = 100 Mb/s, 01 = 200 Mb/s,

10 = 400 Mb/s, and 11 is undefined for this implementation.

ackSent

This field holds the acknowledge sent by the receiver for this packet.

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