LXT970ATC datasheet(35/74 Pages) INTEL

35 / 74 page

Dual-Speed Fast Ethernet Transceiver — LXT970A

Datasheet

2.7

10BASE-T Operation

2.7.1

10BASE-T MII Operations

The MAC transmits data to the LXT970A over the MII interface. The LXT970A converts the

digital data from the MAC into an analog waveform that is transmitted to the network via the

copper interface. The LXT970A converts analog signals received from the network into a digital

format suitable for the MAC. The LXT970A sends the received data to the MAC via the MII. The

5-bit symbol code is not used for 10BASE-T operation. The MII operates only as a 4-bit interface

and the RXD4 & TXD4 lines are not used.

2.7.2

10BASE-T Network Operations

During 10BASE-T operation, the LXT970A transmits and receives Manchester-encoded data

across the network link. When the MAC is not actively transmitting data, the LXT970A sends out

link pulses on the line.

In 10BASE-T mode, the polynomial scrambler/descrambler is inactive. Manchester-encoded

signals received from the network are decoded by the LXT970A and sent across the MII to the

MAC.

The LXT970A does not support fiber connections at 10 Mbps.

2.8

Protocol Sublayer Operations

With respect to the 7-layer communications model, the LXT970A is a Physical Layer 1 (PHY)

device. The LXT970A implements the Physical Coding Sublayer (PCS), Physical Medium

Attachment (PMA), and Physical Medium Dependent (PMD) sublayers of the reference model

defined by the IEEE 802.3u specification. The following paragraphs discuss LXT970A operation

from the reference model point of view.

2.8.1

PCS Sublayer

The Physical Coding Sublayer (PCS) provides the MII interface, as well as the 4B/5B encoding/

decoding function when the MII is operating as a 4B interface.

For 100TX and 100FX operation, the PCS layer provides IDLE symbols to the PMD-layer line

driver as long as TX_EN is de-asserted.

When the MII is operating in 5B mode, the encoder/decoder function is disabled, and symbol data

presented at the MII is transparently passed downstream, and vice versa.

For 10T operation, the PCS layer merely provides a bus interface and serialization/de-serialization

function. 10T operation does not use the 4B/5B encoder, and is not supported when the MII is in

5B mode.

LXT970ATC датащи(PDF) 35 Page - Intel Corporation