L80223 LSI, L80223 Datasheet - Page 38

• Manufacturer Part Number: L80223
• Manufacturer: LSI

Specifications of L80223

• Lead Free Status / RoHS Status: Not Compliant

2.3.8.3 Squelch (100 Mbits/s)
2.3.8.4 Squelch (10 Mbits/s)
2-20
The Squelch block determines if the TP input contains valid data. The
100 Mbits/s TP squelch is one of the criteria used to determine link
integrity. The squelch comparators compare the TP inputs against fixed
positive and negative thresholds called squelch levels. The output from
the squelch comparator goes to a digital squelch circuit, which
determines whether the receive input data on that port is valid. If the data
is invalid, the receiver is in the squelched state. If the input voltage
exceeds the squelch levels at least four times with alternating polarity
within a 10 s interval, the squelch circuit determines that the data is
valid and the receiver enters into the unsquelch state.
In the unsquelch state, the receive threshold level is reduced by
approximately 30% for noise immunity reasons and is called the
unsquelch level. When the receiver is in the unsquelch state, the input
signal is considered valid.
The device stays in the unsquelch state until loss of data is detected.
Loss of data is detected if no alternating polarity unsquelch transitions
are detected during any 10 s interval. When a loss of data is detected,
the receive squelch is turned on again.
The TP squelch algorithm for 10 Mbits/s mode is identical to the
100 Mbits/s mode, except
Functional Description
the 10 Mbits/s TP squelch algorithm is not used for link integrity, but
to sense the beginning of a packet
the receiver goes into the unsquelch state if the input voltage
exceeds the squelch levels for three bit times with alternating polarity
within a 50 to 250 ns interval
the receiver goes into the squelch state when SOI is detected
unsquelch detection has no effect on link integrity (link pulses are
used in 10 Mbits/s mode for that purpose)
start of packet is determined when the receiver goes into the
unsquelch state and CRS is asserted
the receiver meets the squelch requirements defined in IEEE 802.3
Clause 14.
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