TSB21LV03

IEEE 1394-1995 TRIPLE-CABLE TRANSCEIVER/ARBITER

SLLS230A – MARCH 1996 – REVISED DECEMBER 1996

3

POST OFFICE BOX 655303

description (continued)

Four package terminals are used as inputs to set four configuration status bits in the self-identification (Self-ID)

packet. These terminals are hardwired high or low as a function of the equipment design. PC0 – PC2 are the

three terminals that indicate either the need for power from the cable or the ability to supply power to the cable.

The fourth terminal, C/LKON, indicates whether a node is a contender for bus manager. When the C/LKON

terminal is asserted, it means the node can be a contender for bus manager. When the terminal is not asserted,

it means that the node is not a contender. The C bit corresponds to bit 20 in the Self-ID packet, PC0 corresponds

to bit 21, PC1 corresponds to bit 22, and PC2 corresponds to bit 23 (see Table 4–29 of the IEEE 1394–1995

standard for additional details).

A power-down terminal, PD, is provided to allow a power-down mode where most of the TSB21LV03 circuits

are powered down to conserve energy in battery-powered applications. A cable status terminal, CNA, provides

a high output when all twisted-pair cable ports are disconnected. This output is not debounced. The CNA output

can be used to determine when to power the TSB21LV03 down or up. In the power-down mode all circuitry is

disabled except the CNA circuitry. It should be noted that when the device is powered-down it does not act in

a repeater mode.

When the power supply of the TSB21LV03 is removed while the twisted-pair cables are connected, the

TSB21LV03 transmitter and receiver circuitry has been designed to present a high impedance to the cable in

order to not load the TPBias terminal voltage on the other end of the cable.

If the TSB21LV03 is being used with one or more of the ports not being brought out to a connector, the TSB

terminals must be terminated for reliable operation. For each unused port, the TPB+ and TPB– terminals must

be tied together and connected to GND. This is done in the normal termination network. When a port does not

have a cable connected, the normal termination network pulls TPB+ and TPB– to ground through a 5-k

Ω

resistor, thus disabling the port.

NOTE:

All gap counts on all nodes of a 1394 bus must be identical. This may only be accomplished by using

phy configuration packets (see section 4.3.4.3 of IEEE 1394-1995 Standard) or by using two bus

resets, which resets the gap counts to the maximum level (3Fh).

The link power status (LPS) terminal works with the C/LKON terminal to manage the LLC power usage of the

node. The LPS terminal indicates that the LLC of the node is powered down and powers down the phy-LLC

interface to save power. If the phy then receives a link-on packet, the C/LKON terminal is activated to output

a 6.114 MHz signal, which can be used by the LLC to power itself up. Once the LLC is powered up, the LPS

signal communicates this to the TSB21LV03 and the C/LKON signal is turned off and the phy-link interface is

enabled.

Two of the package terminals are used to set up various test conditions used in manufacturing. These terminals,