BCM5208KPF Broadcom, BCM5208KPF Datasheet - Page 10

• Manufacturer Part Number: BCM5208KPF
• Manufacturer: Broadcom

Specifications of BCM5208KPF

• Number Of Receivers: 4
• Data Rate: 10/100Mbps
• Operating Temperature Classification: Commercial
• Operating Supply Voltage (min): 3.14V
• Mounting: Surface Mount
• Operating Temperature (max): 70C
• Operating Temperature (min): 0C
• Lead Free Status / RoHS Status: Not Compliant

n BCM5208
November 3, 1999
CARRIER SENSE
In 100BASE-X modes, carrier sense is asserted asynchronously on the CRS pin as soon as activity is detected in the
receive data stream. RXDV is asserted as soon as a valid start-of-stream delimiter (SSD) is detected. Carrier sense and
RXDV are deasserted synchronously upon detection of a valid end of stream delimiter or two consecutive idle code groups
in the receive data stream. If carrier sense is asserted and a valid SSD is not detected immediately, then RXER will be
asserted in place of RXDV. A value of Eh (E hex) will be driven on the receive data pins to indicate false carrier sense.
In 10BASE-T mode, carrier sense is asserted asynchronously on the CRS pin when valid preamble activity is detected on
the RD+/- input pins.
In half-duplex DTE mode, the BCM5208 will additionally assert carrier sense while transmit enable is asserted and the link
monitor is in the “Pass” state. In repeater or full-duplex mode, CRS is only asserted for receive activity.
COLLISION DETECTION
In half-duplex mode, collision detect is asserted on the COL pin whenever carrier sense is asserted while transmission is
in progress. Collision detect is never asserted in full-duplex mode.
CARRIER INTEGRITY MONITOR
In 100BASE-X repeater applications, it is necessary to protect the repeater core from spurious carrier events generated by
the transceiver. The BCM5208 implements the carrier integrity monitor (CIM) on each port as specified in the IEEE 802.3
standard. When the transceiver detects excessive false carrier events, it will enter the “Disconnect” state, and transmission
and reception will be disabled. The CIM function may be enabled or disabled at reset by a mode select pin, and may be
enabled or disabled following reset through the MII management interface. The CIM function is not enabled in 100BASE-
X DTE or any 10BASE-T mode.
AUTO-NEGOTIATION
The BCM5208 contains the ability to negotiate its mode of operation over the twisted pair link using the Auto-Negotiation
mechanism defined in the IEEE 802.3u specification. Auto-Negotiation may be enabled or disabled by hardware or
software control. When the Auto-Negotiation function is enabled, the BCM5208 will automatically choose its mode of
operation by advertising its abilities and comparing them with those received from its link partner. The BCM5208 can be
configured to advertise 100BASE-TX full-duplex and/or half-duplex and 10BASE-T full and/or half-duplex. Each transceiver
will negotiate independently with its link partner, and choose the highest level of operation available for its own link. Auto-
Negotiation must be disabled during 100BASE-FX operation and will not advertise full-duplex abilities when the device is
configured in repeater mode.
DIGITAL ADAPTIVE EQUALIZER
The digital adaptive equalizer removes interzonal interference created by the transmission channel media. The equalizer
accepts sampled unequalized data from the ADC on each channel and produces equalized data. The BCM5208 achieves
an optimum signal to noise ratio by using a combination of feed forward equalization and decision feedback equalization.
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This powerful technique achieves a 100BASE-TX BER of less than 1 x 10
for transmission up to 100 meters on CAT 5
twisted pair cable, even in harsh noise environments. The digital adaptive equalizers in the BCM5208 achieve performance
close to theoretical limits. The all-digital nature of the design makes the performance very tolerant to on-chip noise. The
filter coefficients are self adapting to any quality of cable or cable length. Due to transmit pre-equalization in 10BASE-T
mode and complete lack of ISI in 100BASE-FX mode, the adaptive equalizer is bypassed in these two modes of operation.
ADC
Each receive channel has its own 6-bit 125 MHz analog to digital converter (ADC). The ADC samples the incoming data
on the receive channel and produces a 6-bit output. The output of the ADC is fed to the digital adaptive equalizer. Advanced
analog circuit techniques achieve low offset, high power supply noise rejection, fast settling time, and low bit error rate.
B r o a d c o m C o r p o r a t i o n
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