TSB41LV06

IEEE 1394a SIX-PORT CABLE TRANSCEIVER/ARBITER

SLLS289 – JANAURY1999

2

POST OFFICE BOX 655303

description (continued)

The TSB41LV06 supports an optional isolation barrier between itself and its LLC. When the ISO input terminal

is tied high, the LLC interface outputs behave normally. When the ISO terminal is tied low, internal differentiating

logic is enabled, and the outputs are driven such that they can be coupled through a capacitive or transformer

galvanic isolation barrier as described in IEEE 1394a section 5.9.4. To operate with TI Bus Holder isolation the

ISO on the PHY terminal must be tied HIGH.

Data bits to be transmitted through the cable ports are received from the LLC on two, four or eight parallel paths

(depending on the requested transmission speed) and are latched internally in the TSB41LV06 in

synchronization with the 49.152 MHz system clock. These bits are combined serially, encoded, and transmitted

at 98.304, 196.608, or 392.216 Mbits/s (referred to as S100, S200, and S400 speed, respectively) as the

outbound data-strobe information stream. During transmission, the encoded data information is transmitted

differentially on the TPB cable pair(s), and the encoded strobe information is transmitted differentially on the

TPA cable pair(s).

During packet reception the TPA and TPB transmitters of the receiving cable port are disabled, and the receivers

for that port are enabled. The encoded data information is received on the TPA cable pair, and the encoded

strobe information is received on the TPB cable pair. The received data-strobe information is decoded to recover

the receive clock signal and the serial data bits. The serial data bits are split into two, four or eight bit parallel

streams (depending upon the indicated receive speed), resynchronized to the local 49.152 MHz system clock

and sent to the associated LLC. The received data is also transmitted (repeated) on the other active (connected)

cable ports.

Both the TPA and TPB cable interfaces incorporate differential comparators to monitor the line states during

initialization and arbitration. The outputs of these comparators are used by the internal logic to determine the

arbitration status. The TPA channel monitors the incoming cable common-mode voltage. The value of this

common-mode voltage is used during arbitration to set the speed of the next packet transmission. In addition,

the TPB channel monitors the incoming cable common-mode voltage on the TPB pair for the presence of the

remotely supplied twisted-pair bias voltage.

The TSB41LV06 provides a 1.86 V nominal bias voltage at the TPBIAS terminal for port termination. The PHY

contains two independent TPBIAS circuits. This bias voltage, when seen through a cable by a remote receiver,

indicates the presence of an active connection. This bias voltage source must be stabilized by an external filter

capacitor of 1

µF.

The line drivers in the TSB41LV06 operate in a high-impedance current mode, and are designed to work with

external 110

Ω line-termination resistor networks in order to match the 110-Ω cable impedance. One network

is provided at each end of a twisted-pair cable. Each network is composed of a pair of series-connected 56-

Ω

resistors. The midpoint of the pair of resistors that is directly connected to the twisted pair A terminals is

connected to its corresponding TPBIAS voltage terminal. The midpoint of the pair of resistors that is directly

connected to the twisted-pair B terminals is coupled to ground through a parallel R-C network with

recommended values of 5 k

Ω and 220 pF. The values of the external line termination resistors are designed

to meet the standard specifications when connected in parallel with the internal receiver circuits. An external

resistor connected between the R0 and R1 terminals sets the driver output current, along with other internal

operating currents. This current setting resistor has a value of 6.3-k

Ω ±0.5%. This may be accomplished by

placing a 6.34-k

Ω ±0.5% resistor in parallel with a 1-MΩ resistor.

When the power supply of the TSB41LV06 is 0 V while the twisted-pair cables are connected, the TSB41LV06

transmitter and receiver circuitry will present a high impedance to the cable and will not load the TPBIAS voltage

at the other end of the cable.