TSB12C01APZ datasheet(35/59 Pages) TI

35 / 59 page

4–5

4.2

Isochronous Transmit (Host Bus to TSB12C01A)

The format of the isochronous-transmit packet is shown in Figure 4–5. The data for each channel must be

presented to the isochronous-transmit FIFO interface in this format in the order that packets are to be sent.

The transmitter sends any packets available at the isochronous-transmit interface immediately following

reception or transmission of the cycle-start message.

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

chanNum

spd

isochronous data

dataLength

TAG

Figure 4–5. Isochronous-Transmit Format

Table 4–5. Isochronous-Transmit Functions

FIELD NAME

DESCRIPTION

dataLength

This field indicates the number of bytes in this packet

TAG

This field indicates the format of data carried by the isochronous packet (00 = formatted, 01 – 11

are reserved).

chanNum

This field carries the channel number with which this data is associated.

spd

This field contains the speed at which to send this packet.

This field carries the transaction layer-specific synchronization bits.

isochronous data

This field contains the data to be sent with this packet. The first byte of data must appear in byte

0 of the first quadlet of this field. If the last quadlet does not contain four bytes of data, the unused

bytes should be padded with zeros.

4.3

Isochronous Receive (TSB12C01A to Host Bus)

The format of the isochronous-receive data is shown in Figure 4–6. The data length, which is found in the

header of the packet, determines the number of bytes in an isochronous packet.

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

chanNum

tCode

isochronous data

dataLength

spd

errCode

TAG

Figure 4–6. Isochronous-Receive Format

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