CS89712-CB View Datasheet(PDF) - Cirrus Logic

Part Name

Description

MFG CO.

CS89712-CB

High-Performance, Low-Power System-on-Chip with 10BASE-T Ethernet Controller

Cirrus Logic 

CS89712

inating the need for external filters or a

filter/transformer hybrid. On-chip filters are gm/c

implementations of fifth-order Butterworth low-

pass filters. Internal tuning circuits keep the gm/c

ratio tightly controlled, even when large tempera-

ture, supply, and IC process variations occur. The

nominal 3 dB cutoff frequency of the filters is

16 MHz, and the nominal attenuation at 30 MHz

(3rd harmonic) is -27 dB.

2.28.2 Transmitter

When configured for 10BASE-T operation,

Manchester encoded data from the ENDEC is fed

into the transmitter’s predistortion circuit where

initial wave shaping and preequalization is per-

formed. The output of the predistortion circuit is

fed into the transmit filter where final wave shaping

occurs and unwanted noise is removed. The signal

then passes to the differential driver where it is am-

plified and driven out of the TXD+/TXD- pins.

In the absence of transmit packets, the transmitter

generates link pulses in accordance with section

14.2.1.1. of the Ethernet standard. Transmitted link

pulses are positive pulses, one bit time wide, typi-

cally generated at a rate of one every 16 ms. The

16 ms timer starts whenever the transmitter com-

pletes an End-of-Frame (EOF) sequence. Thus,

there is a link pulse 16 ms after an EOF unless there

is another transmitted packet. Figure 18 diagrams

the operation of the Link Pulse Generator.

LinkOK

(to MAC)

ENDEC

RXSQL

RX

TX

10BASE-T Transceiver

Link Pulse

Detector

RX Squelch

RX

Comparator

RX Filters

TX Pre-

Distortion

TX Filters

Filter Tuning

TX Drivers

RXD-

RXD+

TXD-

TXD+

Time

Packet

Figure 17. 10BASE-T Transceiver

Packet

Link

Pulse

Link

Pulse

Less Than

16ms

16ms

16ms

Figure 18. Link Pulse Transmission

DS502PP2

53

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