TSB12C01APZ datasheet(37/59 Pages) TI

37 / 59 page

4–7

4.5

CycleMark

The format of the CycleMark data is shown in Figure 4–8. The receiver module inserts a single quadlet to

mark the end of an isochronous cycle. The quadlet is inserted into the receive-FIFO.

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

CyDne

Figure 4–8. CycleMark Format

Table 4–8. CycleMark Functions

FIELD NAME

DESCRIPTION

CyDne

This field indicates the end of an isochronous cycle.

4.6

Phy Configuration

The format of the phy configuration packet is shown in Figure 4–9. The phy configuration packet transmit

contains two quadlets, which are loaded into the ATF. The first quadlet is written to address 80h. The second

quadlet is written to address 8Ch. The 00E0h in the first quadlet tells the TSB12C01A that this is the phy

configuration packet. The Eh is then replaced with 0h before the packet is transmitted to the phy interface.

There is a possibility of a false header error on receipt of a phy configuration packet. If the first 16 bits of

a phy configuration packet (see Figure 4–9) happen to match the destination identifier of a node (bus

number and node number), the TSB12C01A on that node issues a header error since the node misinterprets

the phy configuration packet as a data packet addressed to the node. The suggested solution to this

potential problem is to assign bus numbers that all have the MS bit set to 1. Since the all-ones case is

reserved for addressing the local bus, this leaves only 511 available unique bus identifiers. This is an artifact

of the IEEE 1394-1995 standard.

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

logical inverse of first 16 bits of first quadlet

root_ID

gap_cnt

00 00

11 11

Figure 4–9. Phy Configuration Format

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