TSB12C01APZ datasheet(31/59 Pages) TI

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4–1

4 TSB12C01A Data Formats

The data formats for transmission and reception of data are shown in the following sections. The transmit

format describes the expected organization of data presented to the TSB12C01A at the host-bus interface.

The receive formats describe the data format that the TSB12C01A presents to the host-bus interface.

4.1

Asynchronous Transmit (Host Bus to TSB12C01A)

Asynchronous transmit refers to the use of the asynchronous-transmit FIFO (ATF) interface. The

general-receive FIFO (GRF) is shared by asynchronous data and isochronous data. There are two basic

formats for data to be transmitted and received. The first is for quadlet packets, and the second is for block

packets. For transmits, the FIFO address indicates the beginning, middle, and end of a packet. For receives,

the data length, which is found in the header of the packet, determines the number of bytes in a block packet.

4.1.1

Quadlet Transmit

The quadlet-transmit format is shown in Figure 4–1. The first quadlet contains packet control information.

The second and third quadlets contain the 64-bit, quadlet-aligned address. The fourth quadlet is data used

only for write requests and read responses. For read requests and write responses, the quadlet data field

is omitted.

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

destinationID

destinationOffsetHigh

destinationOffsetLow

quadlet data (for write request and read response)

Figure 4–1. Quadlet-Transmit Format

Table 4–1. Quadlet-Transmit Format

FIELD NAME

DESCRIPTION

spd

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

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

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 IEEE 1394-1995 standard).

priority

The priority level for this packet. For cable implementation, the value of the bits must be 0.

For backplane implementation, see clause 5.4.1.3 and 5.4.2.1 of the IEEE 1394-1995

standard.

destinationID

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

destination node address of this packet.

destination OffsetHigh,

destination OffsetLow

The concatenation of these two fields addresses a quadlet in the destination nodes address

space. This address must be quadlet aligned (modulo 4).

quadlet data

For write requests and read responses, this 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.

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