L-FW802B-DB LSI, L-FW802B-DB Datasheet - Page 3
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L-FW802B-DB
Manufacturer Part Number
L-FW802B-DB
Description
Manufacturer
LSI
Datasheet
1.L-FW802B-DB.pdf
(26 pages)
Specifications of L-FW802B-DB
Lead Free Status / RoHS Status
Compliant
May 2004
Description
The PHY requires either an external 24.576 MHz
crystal or crystal oscillator. The internal oscillator
drives an internal phase-locked loop (PLL), which
generates the required 393.216 MHz reference signal.
The 393.216 MHz reference signal is internally divided
to provide the 49.152 MHz, 98.304 MHz, and
196.608 MHz clock signals that control transmission of
the outbound encoded strobe and data information.
The 49.152 MHz clock signal is also supplied to the
associated LLC for synchronization of the two chips
and is used for resynchronization of the received data.
The powerdown function, when enabled by the PD
signal high, stops operation of the PLL and disables all
circuitry except the cable-not-active (CNA) signal
circuitry.
The PHY supports an isolation barrier between itself
and its LLC. When /ISO is tied high, the link interface
outputs behave normally. When /ISO is tied low,
internal differentiating logic is enabled, and the outputs
become short pulses, which can be coupled through a
capacitor or transformer as described in the
IEEE 1394-1995 Annex J. To operate with bus-keeper
isolation, the /ISO pin of the FW802B must be tied
high.
Data bits to be transmitted through the cable ports are
received from the LLC on two, four, or eight data lines
(D[0:7]), and are latched internally in the PHY in
synchronization with the 49.152 MHz system clock.
These bits are combined serially, encoded, and
transmitted at 98.304 Mbits/s, 196.608 Mbits/s, or
393.216 Mbits/s as the outbound data-strobe
information stream. During transmission, the encoded
data information is transmitted differentially on the TPA
and TPB 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 and
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
(for S100), four (for S200), or eight (for S400) parallel
streams, resynchronized to the local system clock, and
sent to the associated LLC. The received data is also
transmitted (repeated) out of 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
Agere Systems Inc.
(continued)
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 for the
presence of the remotely supplied twisted-pair bias
voltage. This monitor is called bias-detect.
The TPBIAS circuit monitors the value of incoming
TPA pair common-mode voltage when local TPBIAS is
inactive. Because this circuit has an internal current
source and the connected node has a current sink, the
monitored value indicates the cable connection status.
This monitor is called connect-detect.
Both the TPB bias-detect monitor and TPBIAS
connect-detect monitor are used in suspend/resume
signaling and cable connection detection.
The PHY provides a 1.86 V nominal bias voltage for
driver load termination. This bias voltage, when seen
through a cable by a remote receiver, indicates the
presence of an active connection. The value of this
bias voltage has been chosen to allow interoperability
between transceiver chips operating from 5 V or 3 V
nominal supplies. This bias voltage source should be
stabilized by using an external filter capacitor of
approximately 0.33 µF.
The transmitter circuitry, the receiver circuitry, and the
twisted-pair bias voltage circuity are all disabled with a
powerdown condition. The powerdown condition
occurs when the PD input is high. The port transmitter
circuitry, the receiver circuitry, and the TPBIAS output
are also disabled when the port is disabled,
suspended, or disconnected.
The line drivers in the PHY operate in a high-
impedance current mode and are designed to work
with external 112 Ω line-termination resistor networks.
One network is provided at each end of each 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 (TPA) signals is connected to the
TPBIAS voltage signal. The midpoint of the pair of
resistors that is directly connected to the twisted-pair B
(TPB) signals is coupled to ground through a parallel
RC network with recommended resistor and capacitor
values of 5 kΩ and 220 pF, respectively. The value of
the external resistors are specified to meet the
standard specifications when connected in parallel
with the internal receiver circuits.
The driver output current, along with other internal
operating currents, is set by an external resistor. This
resistor is connected between the R0 and R1 signals
and has a value of 2.49 kΩ ± 1%.
Two-Cable Transceiver/Arbiter Device
3