TLF9357

July 1993

DP8391ANS32491A SNI Serial Network Interface

General Description

The DP8391A Serial Network Interface (SNI) provides the

Manchester data encoding and decoding functions for

IEEE 8023 EthernetCheapernet type local area networks

The SNI interfaces the DP8390 Network Interface Controller

(NIC) to the Ethernet transceiver cable When transmitting

the SNI converts non-return-to-zero (NRZ) data from the

controller and clock pulses into Manchester encoding and

sends the converted data differentially to the transceiver

The opposite process occurs on the receive path where a

digital phase-locked loop decodes 10 Mbits signals with as

The DP8391A SNI is a functionally complete Manchester

encoderdecoder including ECL like balanced driver and re-

ceivers on board crystal oscillator collision signal transla-

tor and a diagnostic loopback circuit

The SNI is part of a three chip set that implements the com-

plete IEEE compatible network node electronics as shown

below The other two chips are the DP8392 Coax Transceiv-

er Interface (CTI) and the DP8390 Network Interface Con-

troller (NIC)

Incorporated into the CTI are the transceiver collision and

jabber functions The Media Access Protocol and the buffer

management tasks are performed by the NIC There is an

isolation requirement on signal and power lines between the

CTI and the SNI This is usually accomplished by using a set

of miniature pulse transformers that come in a 16-pin plastic

DIP for signal lines Power isolation however is done by

using a DC to DC converter

Features

Y

Compatible with Ethernet II

IEEE 8023

10Base5

10Base2 and 10Base-T

Y

10 Mbs Manchester encodingdecoding with receive

clock recovery

Y

Patented digital phase locked loop (DPLL) decoder re-

quires no precision external components

Y

Y

Loopback capability for diagnostics

Y

Externally selectable half or full step modes of opera-

tion at transmit output

Y

Squelch circuits at the receive and collision inputs re-

ject noise

Y

High voltage protection at transceiver interface (16V)

Y

TTLMOS compatible controller interface

Y

Connects directly to the transceiver (AUI) cable

Table of Contents

10 System Diagram

20 Block Diagram

30 Functional Description

31

Oscillator

32

Encoder

33

Decoder

34

Collision Translator

35

Loopback

40 Connection Diagrams

50 Pin Descriptions

60 Absolute Maximum Ratings

70 Electrical Characteristics

80 Switching Characteristics

90 Timing and Load Diagrams

100 Physical Dimensions

10 System Diagram

IEEE 8023 Compatible EthernetCheapernet Local Area Network Chip Set

TLF9357 – 1

C1995 National Semiconductor Corporation

RRD-B30M105Printed in U S A