CDB8952 Просмотр технического описания (PDF) - Cirrus Logic

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CDB8952

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

Cirrus Logic 

CS8952T

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

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.

Operating Mode

100BASE-TX Nibble

10BASE-T Nibble

100BASE-TX Symbol

10BASE-T Serial

10BT_SER

0

0

0

1

BPALIGN

0

0

1

Don’t Care

Table 1. Operating Mode Selection

BP4B5B

0

1

Don’t Care

Don’t Care

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.

CIRRUS LOGIC ADVANCED PRODUCT DATABOOK

DS206TPP2

17

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