The TSB41AB1 provides the digital and analog transceiver functions needed to implement a one-port node in
a cable-based IEEE 1394 network. The cable port incorporates one differential line transceiver. The transceiver
includes circuitry to monitor the line conditions as needed for determining connection status, for initialization
and arbitration, and for packet reception and transmission. The TSB41AB1 is designed to interface with a link
layer controller (LLC), such as the TSB12LV21, TSB12LV22, TSB12LV23, TSB12LV26, TSB12LV31,
TSB12LV41, TSB12LV42, or TSB12LV01A.
The TSB41AB1 requires only an external 24.576-MHz crystal as a reference. An external clock may be provided
instead of a crystal. An internal oscillator drives an internal phase-locked loop (PLL), which generates the
required 393.216-MHz reference signal. This reference signal is internally divided to provide the clock signals
used to control transmission of the outbound encoded strobe and data information. A 49.152-MHz clock signal
is supplied to the associated LLC for synchronization of the two chips and is used for resynchronization of the
received data. The power-down (PD) function, when enabled by asserting the PD terminal high, stops operation
of the PLL.
The TSB41AB1 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 Annex J of IEEE Std 1394-1995 and in IEEE 1394a-2000 (section
5.9.4) (hereinafter referred to as Annex J type isolation). To operate with TI bus holder isolation the ISO\ terminal
on the PHY must be high.
Data bits to be transmitted through the cable port are received from the LLC on two, four or eight parallel paths
(depending on the requested transmission speed) and are latched internally in the TSB41AB1 in
synchronization with the 49.152-MHz system clock. These bits are combined serially, encoded, and transmitted
at 98.304, 196.608, or 393.216 Mbits/s (referred to as S100, S200, and S400 speeds, respectively) as the
outbound data-strobe information stream. During transmission, the encoded data information is transmitted
differentially on the TPB cable pair, and the encoded strobe information is transmitted differentially on the TPA
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.
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 TSB41AB1 provides a 1.86-V nominal bias voltage at the TPBIAS terminal for port termination. 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. TPBIAS is typically VDD0.2 V when
the port is not connected to another node.
The line drivers in the TSB41AB1 operate in a high-impedance current mode, and are designed to work with
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±1.0%.
When the power supply of the TSB41AB1 is off while the twisted-pair cables are connected, the TSB41AB1
transmitter and receiver circuitry presents a high impedance to the cable and does not load the TPBIAS voltage
at the other end of the cable. Fail-safe circuitry blocks any leakage path from the port back to the device power
The TESTM, SE, and SM terminals are used to set up various manufacturing test conditions. For normal
operation, the TESTM terminal should be connected to VDD through a 1-k resistor, and SM should be connected directly to ground.
Four package terminals are used as inputs to set the default value for four configuration status bits in the self-ID
packet, and are tied high through a 1-kView datasheet
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