82562EZ Datasheet, PDF (18/40 Pages) Intel Corporation – 82562EZ 10/100 Mbps Platform LAN Connect (PLC)

82562EZ — Networking Silicon
4.1.2.3
MLT-3 Decoder, Descrambler, and Receive Digital Section
The 82562EZ first decodes the MLT-3 data, and then the descrambler reproduces the 5B symbols originated in the
transmitter. The descrambling is based on synchronization to the transmission of the 11-bit Linear Feedback Shift
Register (LFSR) during an idle phase. The data is decoded at the 4B/5B decoder. After the 4B symbols are
obtained, the 82562EZ outputs the receive data to the CSMA unit.
In 100BASE-TX mode, the 82562EZ can detect errors in receive data in a number of ways. Any of the following
conditions is considered an error:
• Link integrity fails in the middle of frame reception.
• The start of stream delimiter “JK” symbol is not fully detected after idle.
• An invalid symbol is detected at the 4B/5B decoder.
• Idle is detected in the middle of a frame (before “TR” is detected).
4.2
10BASE-T Mode
4.2.1
10BASE-T Transmit Blocks
4.2.1.1
10BASE-T Manchester Encoder
After the 2.5 MHz clocked data is serialized in a 10 Mbps serial stream, the 20 MHz clock performs the Manchester
encoding. The Manchester code always has a mid-bit transition. The boundary transition occurs only when the data
is the same from bit to bit. For example, if the value is 11b, then the change is from low to high within the boundary.
4.2.1.2
10BASE-T Driver and Filter
Since 10BASE-T and 100BASE-TX have different filtration needs, both filters are implemented inside the chip.
The 82562EZ supports both technologies through one pair of transmit differential pins and by externally sharing the
same magnetics.
In 10 Mbps mode the line drivers use a pre-distortion algorithm to improve jitter tolerance. The line drivers reduce
their drive level during the second half of “wide” (100 ns) Manchester pulses and maintain a full drive level during
all narrow (50 ns) pulses and the first half of the wide pulses. This reduces line overcharging during wide pulses, a
major source of jitter.
4.2.2
10BASE-T Receive Blocks
4.2.2.1
10BASE-T Manchester Decoder
The 82562EZ performs Manchester decoding and timing recovery in 10BASE-T mode. The Manchester encoded
data stream is decoded from the receive differential pair. This data is transferred to the controller at 2.5 MHz/nibble.
The high-performance circuitry of the 82562EZ exceeds the IEEE 802.3 jitter requirements.
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Datasheet