COM20022I datasheet(3/82 Pages) SMSC

3 / 82 page

10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Board RAM

Datasheet

SMSC COM20022I

Page 3

Revision 02-27-06

DATASHEET

Table of Contents

Chapter 1

General Description................................................................................................................ 6

Chapter 2

Pin Configuration.................................................................................................................... 7

Chapter 3

Description of Pin Functions .................................................................................................. 8

Chapter 4

Protocol Description ............................................................................................................. 11

4.1

Network Protocol ........................................................................................................................................11

4.2

Data Rates .................................................................................................................................................11

4.2.1

Selecting Clock Frequencies Above 2.5 Mbps ....................................................................................12

4.3

Network Reconfiguration ............................................................................................................................12

4.4

Broadcast Messages..................................................................................................................................13

4.5

Extended Timeout Function .......................................................................................................................13

4.5.1

Response Time ...................................................................................................................................13

4.5.2

Idle Time .............................................................................................................................................13

4.5.3

Reconfiguration Time ..........................................................................................................................13

4.6

Line Protocol ..............................................................................................................................................14

4.6.1

Invitations To Transmit........................................................................................................................14

4.6.2

Free Buffer Enquiries ..........................................................................................................................14

4.6.3

Data Packets.......................................................................................................................................14

4.6.4

Acknowledgements .............................................................................................................................15

4.6.5

Negative Acknowledgements ..............................................................................................................15

Chapter 5

System Description ..............................................................................................................16

5.1

Microcontroller Interface.............................................................................................................................16

5.1.1

Selection of 8/16-Bit Access ...............................................................................................................19

5.1.2

DMA Transfers To And From Internal RAM ........................................................................................19

5.1.3

DMA Operation ...................................................................................................................................20

5.1.4

DMA Data Transfer Sequence (I/O to Memory: Read A Packet) ........................................................24

5.1.5

DMA Data Transfer Sequence (Memory to I/O: Write A Packet).........................................................24

5.1.6

High Speed CPU Bus Timing Support ................................................................................................24

5.2

Transmission Media Interface ....................................................................................................................25

5.2.1

Traditional Hybrid Interface .................................................................................................................26

5.2.2

Backplane Configuration .....................................................................................................................26

5.2.3

Differential Driver Configuration ..........................................................................................................28

5.2.4

Programmable TXEN Polarity .............................................................................................................28

Chapter 6

Functional Description..........................................................................................................30

6.1

Microsequencer..........................................................................................................................................30

6.2

Internal Registers .......................................................................................................................................32

6.2.1

Interrupt Mask Register (IMR) .............................................................................................................32

6.2.2

Data Register ......................................................................................................................................33

6.2.3

Tentative ID Register ..........................................................................................................................33

6.2.4

Node ID Register.................................................................................................................................33

6.2.5

Next ID Register..................................................................................................................................34

6.2.6

Status Register....................................................................................................................................34

6.2.7

Diagnostic Status Register ..................................................................................................................34

6.2.8

Command Register .............................................................................................................................34

6.2.9

Address Pointer Registers ..................................................................................................................34

6.2.10

Configuration Register .....................................................................................................................35

6.2.11

Sub-Address Register .....................................................................................................................35

6.2.12

Setup 1 Register..............................................................................................................................35

6.2.13

Setup 2 Register..............................................................................................................................35

6.3

Bus Control Register ..................................................................................................................................36

6.4

DMA Count Register ..................................................................................................................................36

6.5

Internal RAM ..............................................................................................................................................47

6.5.1

Sequential Access Memory.................................................................................................................47

6.5.2

Access Speed .....................................................................................................................................47

6.6

Software Interface ......................................................................................................................................47

6.6.1

Selecting RAM Page Size ...................................................................................................................48

6.6.2

Transmit Sequence .............................................................................................................................49

6.6.3

Receive Sequence ..............................................................................................................................50

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