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PDF COM20020D Data sheet ( Hoja de datos )
| Número de pieza | COM20020D | |
| Descripción | ULANC Revision D Universal Local Area Network Controller | |
| Fabricantes | SMSC Corporation | |
| Logotipo |  |
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COM20020D
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 Package
• 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 -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:
- 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 COM20020D 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 COM20020D
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
1 page  
DIP PIN
NO.
1-3
4-11
23
22
19
20
21
PLCC PIN
DESCRIPTION OF PIN FUNCTIONS
NO.
NAME
SYMBOL
DESCRIPTION
MICROCONTROLLER INTERFACE
1-3
Address
A0/nMUX, Input. On a non-multiplexed mode, A0-A2
0-2
A1,A2/ALE
are address input bits. (A0 is the LSB) On a
multiplexed address/data bus, nMUX tied
Low, A1 is left open, and ALE is tied to the
Address Latch Enable signal. A1 is
connected to an internal pull-up resistor.
4-6,8-12 Data 0-7
AD0-AD2,
D3-D7
Input/Output. On a non-multiplexed bus,
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.
27 nRead/nData nRD/nDS Input. On a 68XX-like bus, nDS is an active
Strobe
low signal issued by the microcontroller as the
data strobe signal to strobe the data onto the
bus. On a 80XX-like bus, nRD is an active
low signal issued by the microcontroller to
indicate a read operation.
26
nWrite/
nWR/DIR Input. On a 68XX-like bus, DIR is issued by
Direction
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, nWR is an
active low signal issued by the microcontroller
to indicate a write operation. In this case, a
logic "0" on this pin, when the COM20020D is
accessed, enables data from the data bus to
be written to the device.
23
nReset in nRESET
Input. This active low signal executes a
hardware reset.
24
nInterrupt nINTR
Output. This active low signal is generated by
the COM20020D when an enabled interrupt
condition occurs.
25 nChip Select nCS
Input. This active low signal selects the
COM20020D for an access.
5
5 Page 
is defined as no line activity and a logic "1" is
defined as a negative pulse of 100nS duration. A
transmission starts with an ALERT BURST
consisting of 6 unit intervals of mark (logic "1").
Eight bit data characters are then sent, with each
character preceded by 2 unit intervals of mark and
one unit interval of space. Five types of
transmission can be performed as described
below:
Invitations To Transmit
An Invitation To Transmit is used to pass the
token from one node to another and is sent by the
following sequence:
• An ALERT BURST
• An EOT (End Of Transmission: ASCII code
04H)
• Two (repeated) DID (Destination ID)
characters
ALERT
EOT
DID
DID
BURST
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
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet COM20020D.PDF ] | |
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