COM20020-5
COM20020-5 ULANC
Universal Local Area Network Controller
with 2K x 8 On-Board RAM
FEATURES
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24-Pin Embedded Network Controller/
Transceiver/RAM
Ideal for Industrial/Factory Automation
and Automotive Applications
Deterministic, 5 Mbps, Token Passing
ARCNET Protocol
Minimal Microcontroller and Media
Interfaces
Flexible Microcontroller Interface for Use
with 80XX, 68XX, etc.
Automatically Detects Type of
Microcontroller Interface:
-Non-Multiplexed or Multiplexed Bus
-Separate nRD & nWR Lines or DIR &
nDS Lines
Full 2Kx8 On-Chip RAM
Command Chaining for Top Performance
Reduced Reconfiguration Times
Sequential Access to Internal RAM
Software Programmable Node ID
Duplicate Node ID Detection
Powerful Diagnostics
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Receive All Mode
Data Rates from 5 Mbps to 312.5 Kbps
24-Pin DIP or 28-Pin PLCC Package
Flexible Media Interface:
- RS485 Differential Driver Interface for
Low Cost, Low Power, High Reliability
- Backplane Mode for Direct Connection to
Media in Short Distance Applications
Eight, 256-Byte Pages Allow 4 Pages TX
and RX Plus Scratch-Pad Memory
No Wait-State Arbitration
Programmable TXEN Polarity
Next ID Readable
Internal Clock Prescaler for Slower Network
Speed without Slowing Arbitration
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Operating Temperature Range of -40 C to
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+85 C
Self-Reconfiguring Protocol
Supports up to 255 Nodes
Supports Various Network Topologies (Star,
Tree, Bus...)
CMOS, Single +5V Supply
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GENERAL DESCRIPTION
SMSC's COM20020-5 is a member of the family
of Industrial Network Controllers from Standard
Microsystems Corporation. The device is a
special 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 COM20020-5
make it the only true network controller
optimized for use in industrial and automotive
applications.
Using an ARCNET protocol
engine is the ideal solution for factory
automation applications because it provides a
token-passing
TABLE OF CONTENTS
FEATURES ......................................................................................................................................................................... 1
GENERAL DESCRIPTION ................................................................................................................................................. 1
PIN CONFIGURATION ....................................................................................................................................................... 3
DESCRIPTION OF PIN FUNCTIONS ................................................................................................................................ 4
PROTOCOL DESCRIPTION .............................................................................................................................................. 8
NETWORK PROTOCOL ............................................................................................................................................. 8
DATA RATES ............................................................................................................................................................... 8
NETWORK RECONFIGURATION .............................................................................................................................. 8
BROADCAST MESSAGES .......................................................................................................................................... 9
EXTENDED TIMEOUT FUNCTION ............................................................................................................................. 9
LINE PROTOCOL....................................................................................................................................................... 10
SYSTEM DESCRIPTION .................................................................................................................................................. 12
MICROCONTROLLER INTERFACE ......................................................................................................................... 12
TRANSMISSION MEDIA INTERFACE ...................................................................................................................... 15
FUNCTIONAL DESCRIPTION ......................................................................................................................................... 18
MICROSEQUENCER ................................................................................................................................................. 18
INTERNAL REGISTERS ............................................................................................................................................ 18
INTERNAL RAM ......................................................................................................................................................... 30
SOFTWARE INTERFACE ......................................................................................................................................... 30
COMMAND CHAINING .............................................................................................................................................. 35
RESET DETAILS ........................................................................................................................................................ 37
INITIALIZATION SEQUENCE .................................................................................................................................... 38
IMPROVED DIAGNOSTICS ...................................................................................................................................... 38
OSCILLATOR ............................................................................................................................................................. 40
OPERATIONAL DESCRIPTION ...................................................................................................................................... 41
MAXIMUM GUARANTEED RATINGS ....................................................................................................................... 41
DC CHARACTERISTICS ........................................................................................................................................... 41
TIMING DIAGRAMS ................................................................................................................................................... 45
ERRATA SHEET............................................................................................................................................................... 57
For more details on the ARCNET protocol engine and traditional dipulse signalling 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.
80 Arkay Drive
Hauppauge, NY 11788
(516) 435-6000
FAX (516) 273-3123
2
protocol, a highly reliable and proven networking
scheme, and a data rate of up to 5 Mbps when
using the COM20020-5.
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 mission critical 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 COM20020-5 the highest performance
industrial communications device available.
With only one COM20020-5 and one
microcontroller, a complete communications
node may be implemented.
ARCNET is a registered trademark of Datapoint Corporation
PIN CONFIGURATION
nRESET IN
nPULSE2
nTXEN
21
nINTR
A0/nMUX
A1
A2/ALE
AD0
AD1
AD2
D3
D4
D5
D6
D7
VSS
1
2
3
4
5
6
7
8
9
10
11
12
23
22
21
20
19
18
17
16
15
14
13
nRD/nDS
nWR/DIR
nWR/DIR
nCS
nINTR
nRESET IN
nTXEN
RXIN
nPULSE2
25
26
27
28
1
2
3
4
5
nCS
24
23
VSS
24
VDD
22
RXIN
20 19
18
17
16
15
14
13
12
nPULSE 1
XTAL2
XTAL1
VDD
VSS
N/C
D7
nRDn/DS
VDD
AO/nMUX
A1
A2/ALE
nPULSE1
AD0
XTAL2
XTAL1
6
7
8
9
10
11
D3
D4
D5
AD1
AD2
Packages: 24-Pin DIP or 28-Pin PLCC
Ordering Information:
COM20020-5
P
PACKAGE TYPE: P = Plastic, LJP = PLCC
TEMP RANGE:
(Blank) = Commercial: 0°C to +70°C
I = Industrial: -40°C to +85°C
DEVICE TYPE: 20020-5 = Universal Local Area Network Controller
(with 2K x 8 RAM)
3
VSS
D6
DESCRIPTION OF PIN FUNCTIONS
DIP PIN
NO.
1-3
PLCC PIN
NO.
1-3
NAME
SYMBOL
DESCRIPTION
MICROCONTROLLER INTERFACE
Address
A0/nMUX,
Input. On a non-multiplexed bus, these
0-2
A1,A2/ALE
signals are directly connected to the low bits
of the host address bus. On a multiplexed
address/data bus, A0/nMUX is tied low, A1
is left open, and A2 is tied to the Address
Latch Enable signal of the host. A1 is
connected to an internal pull-up resistor.
Data 0-7
AD0-AD2,
Input/Output. On a non-multiplexed bus,
D3-D7
these signals are used as the data lines for
the device. On a multiplexed address/data
bus, AD0-AD2 act as the address lines
(latched by ALE) and as the low data lines
for the device. D3-D7 are always used for
data only. These signals are connected to
internal pull-up resistors.
nRead/nDat nRD/nDS
Input. On a 68XX-like bus, this active low
a
signal is issued by the microcontroller as the
nStrobe
data strobe signal to strobe the data onto
the bus. On a 80XX-like bus, this active low
signal is issued by the microcontroller to
indicate a read operation. In this case, a
logic "0" on this pin, when the COM20020-5
is accessed, enables data from the device to
the data bus to be read by the
microcontroller.
nWrite/
nWR/DIR
Input. On a 68XX-like bus, this signal is
Direction
issued by the microcontroller as the
Read/nWrite signal to determine the
direction of data transfer. In this case, a
logic "1" selects a read operation, while a
logic "0" selects a write operation. In this
case, data is actually strobed by the nDS
signal. On an 80XX-like bus, this active low
signal is issued by the microcontroller to
indicate a write operation. In this case, a
logic "0" on this pin, when the COM20020-5
is accessed, enables data from the data bus
to be written to the device.
4-11
4-6,8-12
23
27
22
26
4
DESCRIPTION OF PIN FUNCTIONS
DIP PIN
NO.
19
PLCC PIN
NO.
NAME
23
nReset in
DESCRIPTION
Input. This active low signal issued by the
microcontroller executes a hardware reset.
It is used to activate the internal reset
circuitry within the COM20020-5.
nInterrupt
nINTR
Output. This active low signal is generated
by the COM20020-5 when an enabled
interrupt condition occurs. nINTR returns to
its inactive state when the interrupt status
condition or the corresponding interrupt
mask bit is reset.
nChip Select nCS
Input. This active low signal issued by the
microcontroller selects the COM20020-5 for
an access.
TRANSMISSION MEDIA INTERFACE
nPulse 2,
nPULSE2,
Output. In Normal Mode, these active low
nPulse 1
nPULSE1
signals carry the transmit data information,
encoded in pulse format, from the
COM20020-5 to the media driver circuitry.
When the device is in Backplane Mode, the
nPULSE1 signal driver is programmable
(push/pull or open-drain), while the
nPULSE2 signal provides a clock with
frequency of crystal/4.
nPULSE1 is
connected to a weak internal pull-up resistor
in backplane mode.
Receive In
RXIN
Input. This signal carries the receive data
information from the line receiver circuitry to
the COM20020-5.
nTransmit
nTXEN
Output. This signal is used in Backplane
nEnable
Mode to enable the line drivers for
transmission. The polarity of the signal is
programmable by grounding the nPULSE2
pin. This option is valid only in Backplane
Mode.
SYMBOL
nRESET IN
20
24
21
25
16,15
19,18
17
20
18
21
5
Microchip MCU
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