CS8952T datasheet(17/86 Pages) CIRRUS

17 / 86 page

DS206TPP2

CS8952T

CrystalLAN™ 100BASE-X and 10BASE-T Transceiver

CIRRUS LOGIC ADVANCED PRODUCT DATABOOK

FUNCTIONAL DESCRIPTION

Digital System Interface

The primary digital interface to the CS8952T is an

enhanced IEEE 802.3 Media Independent Interface

(MII). The MII supports parallel data transfer, ac-

cess to the CS8952T Control and Status registers,

and several status and control pins.

For 100BASE-X applications, the digital data in-

terface can be either 4-bit parallel (nibbles) or 5-bit

parallel (symbols). For 10BASE-T applications,

the digital data format can be either 4-bit parallel

(nibbles) or one-bit serial.

While the CS8952T can be fully controlled through

configuration registers via the MII Management

Interface, most fundamental functions can be set at

power-up and reset time through external pins.

Major Operating Modes

The following sections describe the four major op-

erating modes of the CS8952T:

100BASE-TX Nibble Mode

100BASE-X Symbol Modes

10BASE-T Nibble Mode

10BASE-T Serial Mode

The digital interface mode (nibble, symbol, or seri-

al) is selected through input pins 10BT_SER,

BPALIGN and BP4B5B as shown in Table 1.

Table 1. Operating Mode Selection

The choice of operating speed and duplex mode is

made using the auto-negotiation input pins (AN0,

AN1) and/or the auto-negotiation MII registers.

Both speed and duplex modes can either be forced

or negotiated with the link partner as shown in

Table 5 on page 23.

100BASE-TX Nibble Mode

In 100BASE-TX nibble mode, the CS8952T pro-

vides an IEEE 802.3-compliant MII interface. Data

is transferred across the MII in four-bit nibbles.

TX_CLK and RX_CLK are nominally 25 MHz.

Symbol Encoding and Decoding

Four-bit nibble transmit data is encoded into five-

bit symbols for transmission onto the media as

shown in Tables 2 and 3. While this encoding caus-

es the symbol rate transmitted across the wire (125

symbols/second) to be greater than the actual data

rate of the system (100 symbols/second), it is nec-

essary to allow data and control symbols to be sent

consecutively along the same media transparent to

the MAC layer.

Operating Mode

10BT_SER

BPALIGN

BP4B5B

100BASE-TX Nibble

10BASE-T Nibble

000

100BASE-TX Symbol

001

Don’t Care

10BASE-T Serial

Don’t Care

CS8952T Datasheet(PDF) 17 Page - Cirrus Logic

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