Datasheet

4–6

4.2 Asynchronous Receive (TSB12LV01B to Host Bus)

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

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

For block receives, the data length, which is found in the header of the packet, determines the number of

bytes in the packet. All packet formats described in this section refer to the way the packets are stored in

the internal FIFO memory of the TSB12LV01B.

4.2.1 Quadlet Receive

The IEEE 1394-1995 standard specified four types of quadlet receive packets: write request, read request,

write response, and read response packets. Table 4–9 describes the details of each packet.

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

tLabel rt tCode priority

sourceID destinationOffsetHigh

destinationOffsetLow

quadlet data

destinationID

PacCom

spd WriteCount tCode ackSent

Reserved

Figure 4–9. Quadlet-Receive Format (Write Request)

4.2.1.1 Quadlet Write-Request and Read-Request Packets

The format for a quadlet write-request packet is shown in Figure 4–9. The first quadlet read from the GRF

is the packet token described in section 3.3.4. It contains packet-reception status information added by the

TSB12LV01B. The first 16 bits of the second quadlet contains the destination node and bus ID, and the

remaining 16 bits contain the packet control information. The first 16 bits of the third quadlet contain the node

and bus ID of the source, and the remaining 16 bits of the third quadlet and the entire fourth quadlet contain

the 48-bit, quadlet aligned destination offset address. The fifth quadlet contains the data used by the write

request packet. The format for a quadlet read-request packet is shown in Figure 4–10.