4
4
OVERVIEW
The COM20051 is essentially a network board-
in-a-chip. It takes an 80C32 microcontroller core
and an ARCNET controller and integrates them
into a single device.
ARCNET is a token
passing-based protocol that combines powerful
flow control, error detection, and diagnostic
capabilities to deliver fast and reliable messages.
The COM20051 supports a variety of data rates
(5 Mbps to 156 Kbps), topologies (bus, star,
tree), and media types (RS-485, coax, twisted
pair, fiber optic, and powerline) to suit any type of
application.
The ARCNET network core of the COM20051
contains many features that make network
development simple and easy to comprehend.
Diagnostic
features,
such
as
Receive
All,
Duplicate
ID
Detection,
Reconfiguration
Detection, Token, and Receiver Detection, all
combine to make the COM20051 simple to use
and to implement in any environment.
The
ARCNET protocol itself is relatively simple to
understand and very flexible. A wide variety of
support products are available to assist in
network development, such as software drivers,
line drivers, boards, and development kits. The
COM20051 implements a full-featured 16MHz,
Intel-compatible 80C32 microcontroller with all of
the standard peripheral functions, including a full
duplex serial port, two timer/counters, one 8-bit
general purpose digital I/O port, and interrupt
controller. The 8051 architecture has long been
a standard in the embedded control industry for
low-level data acquisition and control. ARCNET
and the 8051 form a simple solution for many of
today's and tomorrow's low-level networking
solutions.
In addition to the 80C32 and the ARCNET
network core, the COM20051 contains all the
address decoding and interrupt routing logic to
interface the network core to the 80C32 core.
The
integrated
8051/ARCNET
combination
provides an extremely cost-effective and space-
efficient
solution
for
industrial
networking
applications. The COM20051 can be used in a
stand-alone embedded application, executing
control algorithms or performing data acquisition
and communicating data in a master/slave or
peer-to-peer configuration, or used as a slave
processor handling communication tasks in a
multi-processing system.
DESCRIPTION OF PIN FUNCTIONS
PIN NO.
NAME
SYMBOL
DESCRIPTION
1
Receive In
RXIN
Input. Network receiver input.
2-9
P1.0-1.7
P1.0-1.7
Input/Output. Port 1 of the 8051. General purpose
digital I/O port.
10
Reset
RESET
Input. Active high reset.
11
P3.0
P3.0
Input/Output. Port 3 bit 0 of the 8051. RX input of
serial port.
12
nPulse 1
nPULSE1
Output. Network output. Open-drain when
backplane mode is invoked, otherwise it is a push-
pull output.
13-19
P3.1-3.7
P3.1-3.7
Input/Output. Port 3 bits 1-7 of the 8051.
20, 21
Crystal Oscillator XTAL1,
XTAL2
Input. Oscillator inputs 1 and 2.
22
Ground
VSS
Ground pin.
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