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COM20019 Schematic ( PDF Datasheet ) - SMSC Corporation

Teilenummer COM20019
Beschreibung Low Cost ARCNET (ANSI 878.1) Controller
Hersteller SMSC Corporation
Logo SMSC Corporation Logo 




Gesamt 30 Seiten
COM20019 Datasheet, Funktion
COM20019
www.DataSheet4U.com
Low Cost ARCNET (ANSI 878.1) Controller with 2K x 8
On-Board RAM
FEATURES
New Features
- Data Rates up to 312.5 Kbps
- 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 for Adjusting Network
Speed
Operating Temperature Range of -40oC to
+85oC
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:
- RS485 Differential Driver Interface For
Low Cost, Low Power, High Reliability
GENERAL DESCRIPTION
SMSC's COM20019 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 COM20019
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
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COM20019 Datasheet, Funktion
DIP PIN
NO.
16,15
17
18
13,14
24
12
PLCC PIN
NO.
NAME
SYMBOL
DESCRIPTION
TRANSMISSION MEDIA INTERFACE
19,18 nPulse 2,
nPulse 1
nPULSE2,
nPULSE1
Output (nPULSE1), Input/Output (nPULSE2).
In Normal Mode, these active low signals
carry the transmit data information, encoded
in pulse format, as DIPULSE waveform.
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
double the data rate. nPULSE1 is connected
to a weak internal pull-up resistor on the
open/drain driver in backplane mode. The
COM20019 does not support the Normal
Mode. Use only in the Backplane Mode.
20 Receive In RXIN
Input. This signal carries the receive data
information from the line tranceiver.
21 nTransmit nTXEN
nEnable
Output. This signal is used prior to the Power-
up to enable the line drivers for transmission.
The polarity of the signal is programmable
through the nPULSE2 pin.
nPULSE2 floating before Power-up: nTXEN
active low (Default option)
nPULSE2 grounded before Power-up:
nTXEN active high (This option is only
available in Backplane Mode)
16,17 Crystal
Oscillator
XTAL1,
XTAL2
An external crystal should be connected to
these pins. Oscillation frequency range is
from 10 to 20 MHz. If an external TTL clock is
used instead, it must be connected to XTAL1
with a 390 pull-up resistor, and XTAL2
should be left floating.
15,28 Power
Supply
VDD
+5 Volt Power Supply pin.
7,14,22 Ground
VSS
Ground pin.
6
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6 Page









COM20019 pdf, datenblatt
Free Buffer Enquiries
A Free Buffer Enquiry is used to ask another node
if it is able to accept a packet of data. It is sent by
the following sequence:
An ALERT BURST
An ENQ (ENQuiry: ASCII code 85H)
Two (repeated) DID (Destination ID) characters
ALERT
BURST
ENQ
DID
DID
Data Packets
A Data Packet consists of the actual data being
sent to another node. It is sent by the following
sequence:
An ALERT BURST
An SOH (Start Of Header--ASCII code 01H)
An SID (Source ID) character
Two (repeated) DID (Destination ID)
characters
A single COUNT character which is the 2's
complement of the number of data bytes to
follow if a short packet is sent, or 00H
followed by a COUNT character if a long
packet is sent.
N data bytes where COUNT = 256-N (or 512-
N for a long packet)
Two CRC (Cyclic Redundancy Check)
characters. The CRC polynomial used is:
X16 + X15 + X2 + 1.
ALERT
BURST
SOH
SID DID DID
COUNT
data
data CRC CRC
Acknowledgements
An Acknowledgement is used to acknowledge
reception of a packet or as an affirmative
response to FREE BUFFER ENQUIRIES and is
sent by the following sequence:
An ALERT BURST
An ACK (ACKnowledgement--ASCII code
86H) character
ALERT BURST
ACK
Negative Acknowledgements
A Negative Acknowledgement is used as a
negative response to FREE BUFFER
ENQUIRIES and is sent by the following
sequence:
An ALERT BURST
A NAK (Negative Acknowledgement--ASCII
code 15H) character
ALERT BURST
NAK
12
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12 Page





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