LAN8710AI datasheet(25/82 Pages) MICROCHIP

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Small Footprint MII/RMII 10/100 Ethernet Transceiver with HP Auto-MDIX and flexPWR® Technology

Datasheet

SMSC LAN8710A/LAN8710Ai

Revision 1.4 (08-23-12)

DATASHEET

than “00” on TXD[1:0] while TXEN is deasserted shall be ignored by the device.TXD[1:0] shall provide

valid data for each REF_CLK period while TXEN is asserted.

In order to comply with legacy 10BASE-T MAC/Controllers, in half-duplex mode the transceiver loops

back the transmitted data, on the receive path. This does not confuse the MAC/Controller since the

COL signal is not asserted during this time. The transceiver also supports the SQE (Heartbeat) signal.

See Section 3.8.7, "Collision Detect," on page 42, for more details.

3.1.3.2

Manchester Encoding

The 4-bit wide data is sent to the 10M TX block. The nibbles are converted to a 10Mbps serial NRZI

data stream. The 10M PLL locks onto the external clock or internal oscillator and produces a 20MHz

clock. This is used to Manchester encode the NRZ data stream. When no data is being transmitted

(TXEN is low), the 10M TX block outputs Normal Link Pulses (NLPs) to maintain communications with

the remote link partner.

3.1.3.3

10M Transmit Drivers

The Manchester encoded data is sent to the analog transmitter where it is shaped and filtered before

being driven out as a differential signal across the TXP and TXN outputs.

3.1.4

10BASE-T Receive

The 10BASE-T receiver gets the Manchester- encoded analog signal from the cable via the magnetics.

It recovers the receive clock from the signal and uses this clock to recover the NRZI data stream. This

10M serial data is converted to 4-bit data nibbles which are passed to the controller via MII at a rate

of 2.5MHz.

This 10M receiver uses the following blocks:

Filter and SQUELCH (analog)

10M PLL (analog)

RX 10M (digital)

MII (digital)

3.1.4.1

10M Receive Input and Squelch

The Manchester signal from the cable is fed into the transceiver (on inputs RXP and RXN) via 1:1 ratio

magnetics. It is first filtered to reduce any out-of-band noise. It then passes through a SQUELCH

circuit. The SQUELCH is a set of amplitude and timing comparators that normally reject differential

voltage levels below 300mV and detect and recognize differential voltages above 585mV.

3.1.4.2

Manchester Decoding

The output of the SQUELCH goes to the 10M RX block where it is validated as Manchester encoded

data. The polarity of the signal is also checked. If the polarity is reversed (local RXP is connected to

RXN of the remote partner and vice versa), the condition is identified and corrected. The reversed

condition is indicated by the XPOL bit of the Special Control/Status Indications Register. The 10M PLL

is locked onto the received Manchester signal, from which the 20MHz cock is generated. Using this

clock, the Manchester encoded data is extracted and converted to a 10MHz NRZI data stream. It is

then converted from serial to 4-bit wide parallel data.

The 10M RX block also detects valid 10Base-T IDLE signals - Normal Link Pulses (NLPs) - to maintain

the link.

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