COM20020ID
COM20020 ULANC
Revision D
Universal Local Area Network Controller
with 2K x 8 On-Board RAM
FEATURES
New Features for Rev. D
-
Data Rates up to 5 Mbps
-
Programmable Reconfiguration Times
24 Pin DIP, 28 Pin PLCC, 48 Pin TQFP
Packages
Ideal for Industrial/Factory/Building
Automation and Transportation
Applications
Deterministic, (ANSI 878.1), Token Passing
ARCNET Protocol
Minimal Microcontroller and Media
Interface Logic Required
Flexible Interface For Use With All
Microcontrollers or Microprocessors
Automatically Detects Type of
Microcontroller Interface
2Kx8 On-Chip Dual Port RAM
Command Chaining for Packet Queuing
Sequential Access to Internal RAM
Software Programmable Node ID
Eight, 256 Byte Pages Allow Four Pages TX
and RX Plus Scratch-Pad Memory
Next ID Readable
Internal Clock Scaler and Clock Multiplier for
Adjusting Network Speed
Operating Temperature Range of -40
o
C to
+85
o
C
Self-Reconfiguration
Protocol
Supports up to 255 Nodes
Supports Various Network Topologies (Star,
Tree, Bus...)
CMOS, Single +5V Supply
Duplicate Node ID Detection
Powerful
Diagnostics
Receive All Packets Mode
Flexible Media Interface:
-
Traditional Hybrid Interface For Long
Distances up to Four Miles at 2.5Mbps.
-
RS485 Differential Driver Interface For
Low Cost, Low Power, High Reliability
GENERAL DESCRIPTION
SMSC's COM20020ID is a member of the family
of Embedded ARCNET Controllers from Standard
Microsystems Corporation. The device is a
general purpose communications controller for
networking microcontrollers and intelligent
peripherals in industrial, automotive, and
embedded control environments using an
ARCNET
protocol engine. The small 24 pin
package, flexible microcontroller and media
interfaces, eight- page message support, and
extended temperature range of the COM20020ID
make it the only true network controller optimized
for use in industrial, embedded, and automotive
applications. Using an ARCNET protocol engine
is the ideal solution for embedded control
applications because it provides a deterministic
token-passing protocol, a highly reliable and
2
proven networking scheme, and a data rate of up
to 5 Mbps when using the COM20020ID.
A token-passing protocol provides predictable
response times because each network event
occurs within a predetermined time interval, based
upon the number of nodes on the network. The
deterministic nature of ARCNET is essential in
real time applications. The integration of the 2Kx8
RAM buffer on-chip, the Command Chaining
feature, the 5 Mbps maximum data rate, and the
internal diagnostics make the COM20020ID the
highest performance embedded communications
device available. With only one COM20020ID and
one microcontroller, a complete communications
node may be implemented.
ORDERING INFORMATION
Order Numbers:
COM20020ILJP
28 pin PLCC Package
COM20020IP
24 pin DIP Package
COM20020I-HD
48 pin TQFP Package
3
TABLE OF CONTENTS
FEATURES.............................................................................................................................................. 1
GENERAL DESCRIPTION ...................................................................................................................... 1
PIN CONFIGURATIONS.......................................................................................................................... 4
DESCRIPTION OF PIN FUNCTIONS ...................................................................................................... 6
PROTOCOL DESCRIPTION ................................................................................................................... 9
NETWORK PROTOCOL ..................................................................................................................... 9
DATA RATES...................................................................................................................................... 9
NETWORK RECONFIGURATION .................................................................................................... 10
BROADCAST MESSAGES ............................................................................................................... 11
EXTENDED TIMEOUT FUNCTION .................................................................................................. 11
LINE PROTOCOL ............................................................................................................................. 11
SYSTEM DESCRIPTION ....................................................................................................................... 14
MICROCONTROLLER INTERFACE................................................................................................. 14
TRANSMISSION MEDIA INTERFACE.............................................................................................. 18
FUNCTIONAL DESCRIPTION .............................................................................................................. 23
MICROSEQUENCER........................................................................................................................ 23
INTERNAL REGISTERS ................................................................................................................... 26
INTERNAL RAM................................................................................................................................ 39
COMMAND CHAINING ..................................................................................................................... 44
INITIALIZATION SEQUENCE ........................................................................................................... 46
IMPROVED DIAGNOSTICS.............................................................................................................. 47
OPERATIONAL DESCRIPTION............................................................................................................ 50
MAXIMUM GUARANTEED RATINGS* ............................................................................................. 50
DC ELECTRICAL CHARACTERISTICS ........................................................................................... 50
TIMING DIAGRAMS .............................................................................................................................. 53
APPENDIX A ......................................................................................................................................... 69
APPENDIX B: EXAMPLE OF INTERFACE CIRCUIT DIAGRAM TO ISA BUS .................................. 73
APPENDIX C ......................................................................................................................................... 74
SOFTWARE IDENTIFICATION OF THE COM20020 REV B, REV C AND REV D .............................. 74
COM20020ID REVISIONS..................................................................................................................... 75
For more details on the ARCNET protocol engine and traditional dipulse signaling schemes,
please refer to the ARCNET Local Area Network Standard, available from Standard Microsystems
Corporation or the ARCNET Designer's Handbook, available from Datapoint Corporation.
For more detailed information on cabling options including RS485, transformer-coupled RS-485
and Fiber Optic interfaces, please refer to the following technical note which is available from
Standard Microsystems Corporation: Technical Note 7-5 - Cabling Guidelines for the COM20020
ULANC.
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