SMSC COM20022I3V-HD 10 mbps arcnet (ansi 878.1) controller with 2kx8 on-chip ram Datasheet

COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI
878.1) Controller with
2Kx8 On-Chip RAM
Datasheet
Product Features
New Features
ƒ
− Data Rates up to 10 Mbps
− Selectable 8/16 Bit Wide Bus With Data Swapper
− Programmable Reconfiguration Times
Eight, 256 Byte Pages Allow Four Pages TX and
RX Plus Scratch-Pad Memory
ƒ
Next ID Readable
ƒ
Internal Clock Scaler and Clock Multiplier for
Adjusting Network Speed
ƒ
Operating Temperature Range of -40oC to +85oC
Ideal for Industrial/Factory/Building Automation
and Transportation Applications
ƒ
3.3V power supply with 5V tolerant I/O
ƒ
Deterministic, (ANSI 878.1), Token Passing
ARCNET Protocol
ƒ
Self-Reconfiguration Protocol
ƒ
Supports up to 255 Nodes
ƒ
Minimal Microcontroller and Media Interface
Logic Required
ƒ
Supports Various Network Topologies (Star,
Tree, Bus...)
ƒ
Flexible Interface For Use With All
Microcontrollers or Microprocessors
ƒ
CMOS, Single +3.3V Supply
ƒ
Duplicate Node ID Detection
ƒ
Automatically Detects Type of Microcontroller
Interface
ƒ
Powerful Diagnostics
ƒ
ƒ
Receive All Packets Mode
2Kx8 On-Chip Dual Port RAM
ƒ
ƒ
Command Chaining for Packet Queuing
ƒ
Sequential Access to Internal RAM
ƒ
Software Programmable Node ID
ƒ
ƒ
ƒ
48 Pin TQFP Package; Lead-Free RoHS
Compliant package also available
Flexible Media Interface:
− Traditional Hybrid Interface For Long Distances
at 2.5Mbps
− RS485 Differential Driver Interface For Low Cost,
Low Power, High Reliability
ORDERING INFORMATION
Order Number:
COM20022I3V-HD for 48 pin TQFP package
COM20022I3V-HT for 48 pin, TQFP Lead-Free RoHS Compliant package
SMSC COM20022I 3.3V Rev.C
Page 1
DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
80 ARKAY DRIVE, HAUPPAUGE, NY 11788 (631) 435-6000, FAX (631) 273-3123
Copyright © 2007 SMSC or its subsidiaries. All rights reserved.
Circuit diagrams and other information relating to SMSC products are included as a means of illustrating typical applications. Consequently, complete
information sufficient for construction purposes is not necessarily given. Although the information has been checked and is believed to be accurate, no
responsibility is assumed for inaccuracies. SMSC reserves the right to make changes to specifications and product descriptions at any time without
notice. Contact your local SMSC sales office to obtain the latest specifications before placing your product order. The provision of this information does
not convey to the purchaser of the described semiconductor devices any licenses under any patent rights or other intellectual property rights of SMSC
or others. All sales are expressly conditional on your agreement to the terms and conditions of the most recently dated version of SMSC's standard
Terms of Sale Agreement dated before the date of your order (the "Terms of Sale Agreement"). The product may contain design defects or errors
known as anomalies which may cause the product's functions to deviate from published specifications. Anomaly sheets are available upon request.
SMSC products are not designed, intended, authorized or warranted for use in any life support or other application where product failure could cause
or contribute to personal injury or severe property damage. Any and all such uses without prior written approval of an Officer of SMSC and further
testing and/or modification will be fully at the risk of the customer. Copies of this document or other SMSC literature, as well as the Terms of Sale
Agreement, may be obtained by visiting SMSC’s website at http://www.smsc.com. SMSC is a registered trademark of Standard Microsystems
Corporation (“SMSC”). Product names and company names are the trademarks of their respective holders.
SMSC DISCLAIMS AND EXCLUDES ANY AND ALL WARRANTIES, INCLUDING WITHOUT LIMITATION ANY AND ALL IMPLIED WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE, AND AGAINST INFRINGEMENT AND THE LIKE, AND ANY AND
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DIRECT, INCIDENTAL, INDIRECT, SPECIAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES; OR FOR LOST DATA, PROFITS, SAVINGS OR
REVENUES OF ANY KIND; REGARDLESS OF THE FORM OF ACTION, WHETHER BASED ON CONTRACT; TORT; NEGLIGENCE OF SMSC
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HAVE FAILED OF ITS ESSENTIAL PURPOSE, AND WHETHER OR NOT SMSC HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
DAMAGES.
Revision 03-08-07
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DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
TABLE OF CONTENTS
Chapter 1
General Description ............................................................................................................. 6
Chapter 2
Pin Configuration................................................................................................................. 7
Chapter 3
Description of Pin Functions ............................................................................................... 8
Chapter 4
Protocol Description........................................................................................................... 11
4.1
4.2
Network Protocol ............................................................................................................................... 11
Data Rates......................................................................................................................................... 11
4.2.1
4.3
4.4
4.5
4.5.1
4.5.2
4.5.3
4.6
Chapter 5
Chapter 6
Traditional Hybrid Interface.....................................................................................................................21
Backplane Configuration.........................................................................................................................21
Differential Driver Configuration..............................................................................................................23
Programmable TXEN Polarity.................................................................................................................23
Functional Description....................................................................................................... 25
Interrupt Mask Register (IMR) ................................................................................................................27
Data Register..........................................................................................................................................27
Tentative ID Register ..............................................................................................................................27
Node ID Register ....................................................................................................................................28
Next ID Register .....................................................................................................................................28
Status Register .......................................................................................................................................28
Diagnostic Status Register .....................................................................................................................28
Command Register.................................................................................................................................28
Address Pointer Registers ......................................................................................................................29
Configuration Register ........................................................................................................................29
Sub-Address Register .........................................................................................................................29
Setup 1 Register .................................................................................................................................29
Setup 2 Register .................................................................................................................................29
Bus Control Register ...........................................................................................................................30
Internal RAM...................................................................................................................................... 39
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
6.4
Selection of 8/16-Bit Access ...................................................................................................................19
High Speed CPU Bus Timing Support ....................................................................................................19
Microsequencer................................................................................................................................. 25
Internal Registers .............................................................................................................................. 27
6.2.1
6.2.2
6.2.3
6.2.4
6.2.5
6.2.6
6.2.7
6.2.8
6.2.9
6.2.10
6.2.11
6.2.12
6.2.13
6.2.14
6.3
System Description............................................................................................................. 16
Transmission Media Interface ........................................................................................................... 21
5.2.1
5.2.2
5.2.3
5.2.4
6.1
6.2
Invitations To Transmit ...........................................................................................................................14
Free Buffer Enquiries..............................................................................................................................14
Data Packets ..........................................................................................................................................14
Acknowledgements.................................................................................................................................15
Negative Acknowledgements .................................................................................................................15
Microcontroller Interface.................................................................................................................... 16
5.1.1
5.1.2
5.2
Response Time.......................................................................................................................................13
Idle Time.................................................................................................................................................13
Reconfiguration Time..............................................................................................................................13
Line Protocol ..................................................................................................................................... 13
4.6.1
4.6.2
4.6.3
4.6.4
4.6.5
5.1
Selecting Clock Frequencies Above 2.5 Mbps .......................................................................................11
Network Reconfiguration ................................................................................................................... 12
Broadcast Messages......................................................................................................................... 13
Extended Timeout Function .............................................................................................................. 13
Sequential Access Memory ....................................................................................................................39
Access Speed.........................................................................................................................................40
Software Interface...................................................................................................................................40
Selecting RAM Page Size.......................................................................................................................40
Transmit Sequence.................................................................................................................................42
Receive Sequence..................................................................................................................................43
Command Chaining........................................................................................................................... 44
SMSC COM20022I 3.3V Rev.C
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DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
6.4.1
6.4.2
6.4.3
6.5
Transmit Command Chaining .................................................................................................................45
Receive Command Chaining ..................................................................................................................45
Reset Details ..........................................................................................................................................46
Initialization Sequence ...................................................................................................................... 46
6.5.1
6.6
Bus Determination ..................................................................................................................................46
Improved Diagnostics........................................................................................................................ 47
6.6.1
6.6.2
6.6.3
Normal Results: ......................................................................................................................................48
Abnormal Results: ..................................................................................................................................48
Oscillator.................................................................................................................................................48
Chapter 7
7.1
7.2
Operational Description .................................................................................................... 50
Maximum Guaranteed Ratings* ........................................................................................................ 50
DC Electrical Characteristics............................................................................................................. 50
Chapter 8
Timing Diagrams................................................................................................................ 53
Chapter 9
Appendix A ......................................................................................................................... 69
9.1
9.2
NOSYNC Bit ...................................................................................................................................... 69
EF Bit................................................................................................................................................. 69
Chapter 10
Appendix B ...................................................................................................................... 72
Chapter 11
Appendix C...................................................................................................................... 73
11.1
Software Identification of the COM20022I 3V Rev B and Rev C................................................... 73
Revision 03-08-07
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DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
LIST OF FIGURES
Figure 3.1 - COM20022I 3V Operation ........................................................................................................................10
Figure 5.1 - Multiplexed, 8051 - Like Bus Interface with RS-485 Interface .....................................................................17
Figure 5.2 - Non-Multiplexed, 6801-Like Bus Interface with RS-485 Interface ...............................................................18
Figure 5.3 - High Speed CPU Bus Timing – Intel CPU Mode ......................................................................................20
Figure 5.4 - COM20022I 3V Network Using RS-485 Differential Transceivers...............................................................22
Figure 5.5 - Dipluse Waveform for Data of 1-1-0 ...........................................................................................................22
Figure 5.6 - Internal Block Diagram...............................................................................................................................24
Figure 6.1 - Sequential Access Operation.....................................................................................................................39
Figure 6.2 - RAM Buffer Packet Configuration ..............................................................................................................42
Figure 6.3 - Command Chaining Status Register Queue...............................................................................................44
Figure 7.1 - AC Measurements ....................................................................................................................................52
Figure 8.1 - Multiplexed Bus, 68XX-Like Control Signals; Read Cycle ........................................................................53
Figure 8.2 - Multiplexed Bus, 80XX-Like Control Signals; Read Cycle ........................................................................54
Figure 8.3 - Multiplexed Bus, 68XX-Like Control Signals; Write Cycle.........................................................................55
Figure 8.4 - Multiplexed Bus, 80XX-Like Control Signals; Write Cycle.........................................................................56
Figure 8.5 - Non-Multiplexed Bus, 80XX-Like Control Signals; Read Cycle.................................................................57
Figure 8.6 - Non-Multiplexed Bus, 80XX-Like Control Signals; Read Cycle.................................................................58
Figure 8.7 - Non-Multiplexed Bus, 68XX-Like Control Signals; Read Cycle.................................................................59
Figure 8.8 - Non-Multiplexed Bus, 68XX-Like Control Signals; Read Cycle.................................................................60
Figure 8.9 - Non-Multiplexed Bus, 80XX-Like Control Signals; Write Cycle.................................................................61
Figure 8.10 - Non-Multiplexed Bus, 80XX-Like Control Signals; Write Cycle ...............................................................62
Figure 8.11 - Non-Multiplexed Bus, 68XX-Like Control Signals; Write Cycle ...............................................................63
Figure 8.12 - Non-Multiplexed Bus, 68XX-Like Control Signals; Write Cycle ...............................................................64
Figure 8.13 - Normal Mode Transmit or Receive Timing..............................................................................................65
Figure 8.14 - Backplane Mode Transmit or Receive Timing ........................................................................................66
Figure 8.15 - TTL Input Timing on XTAL1 Pin..............................................................................................................67
Figure 8.16 - Reset and Interrupt Timing .....................................................................................................................67
Figure 8.17 - 48 Pin TQFP Package Outline ................................................................................................................68
Figure 9.1 - Effect of the EF Bit on the TA/RI Bit..........................................................................................................71
Figure 10.1 - Example of Interface of Circuit Diagram to ISA Bus................................................................................72
LIST OF TABLES
Table 5.1 - Typical Media .............................................................................................................................................24
Table 6.1 - Read Register Summary............................................................................................................................25
Table 6.2 - Data Register at 16 Bit Access ..................................................................................................................26
Table 6.3 - Write Register Summary ............................................................................................................................26
Table 6.4 - Data Register at 16 Bit Address .................................................................................................................26
Table 6.5 - Status Register ...........................................................................................................................................30
Table 6.6 - Diagnostic Status Register..........................................................................................................................31
Table 6.7 - Command Register.....................................................................................................................................32
Table 6.8 - Address Pointer High Register ....................................................................................................................33
Table 6.9 - Address Pointer Low Register.....................................................................................................................33
Table 6.10 - Sub Address Register ...............................................................................................................................34
Table 6.11 - Configuration Register ..............................................................................................................................34
Table 6.12 - Setup 1 Register .......................................................................................................................................36
Table 6.13 - Setup 2 Register .......................................................................................................................................37
Table 6.14 - Bus Control Register.................................................................................................................................38
Table 8.1 - 48 Pin TQFP Package Parameters ............................................................................................................68
SMSC COM20022I 3.3V Rev.C
Page 5
DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Chapter 1
General Description
SMSC's COM20022I 3V 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 and embedded control environments using an
ARCNET protocol engine. The small 48 pin package, flexible microcontroller and media interfaces, eightpage message support, and extended temperature range of the COM20022I 3V make it the only true
network controller optimized for use in industrial and embedded applications. Using an ARCNET protocol
engine is the ideal solution for embedded control applications because it provides a deterministic tokenpassing protocol, a highly reliable and proven networking scheme, and a data rate of up to 10 Mbps when
using the COM20022I 3V. 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 10 Mbps maximum data rate, and the
internal diagnostics make the COM20022I 3V the highest performance embedded communications device
available. With only one COM20022I 3V and one microcontroller, a complete communications node may
be implemented.
NOTE:
For more details on the ARCNET protocol engine and traditional dipulse signaling schemes, please
refer to the ARCNET Local Area Network Standard, or the ARCNET Designer's Handbook, available
from Datapoint Corporation.
Revision 03-08-07
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DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
VSS
nREFEX
nRD/nDS
TC
nWR/DIR
45
nIOCS16
46
VDD
A1
D8
47
A0/nMUX
48
A2/ALE
Pin Configuration
D9
Chapter 2
44
43
42
41
40
39
38
37
AD0
1
36
nCS
AD1
2
35
nDACK
D10
3
34
nINTR
AD2
4
33
DREQ
D11
5
32
VDD
VSS
6
31
nRESET
D3
7
30
VSS
VDD
8
29
nTXEN
D4
9
28
RXIN
D5
10
27
N/C
VSS
11
26
BUSTMG
D6
12
25
nPULSE2
COM20022I
COM200223V
48Pin
Pin TQFP
TQFP
48
24
nPULSE1
23
VSS
22
XTAL2
21
XTAL1
20
VDD
19
N/C
18
VSS
17
D15
16
D14
15
D13
14
D12
D7
13
Ordering Information:
COM20022
PACKAGE TYPE: TQFP
TEMP RANGE:
(Blank) = Commercial: 0°C to +70°C
I = Industrial: -40°C to +85°C
DEVICE TYPE: 20022 = Universal Local Area Network Controller
(with 2K x 8 RAM)
SMSC COM20022I 3.3V Rev.C
Page 7
DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Chapter 3
PIN NO
Description of Pin Functions
NAME
44,45,
46
Address
0-2
1,2,4,
7,9,
10,12,
13
Data 0-7
47, 48,
3,5,
14-17
Data 8-15
37
nWrite/
Direction
39
nRead/
nData
Strobe
31
34
36
nReset In
nInterrupt
nChip
Select
nI/O
16 Bit
Indicator
42
26
Revision 03-08-07
Read/Write
Bus Timing
Select
SYMBOL
I/O
DESCRIPTION
MICROCONTROLLER INTERFACE
IN
A0/nMUX
On a non-multiplexed mode, A0-A2 are address
input bits. (A0 is the LSB) On a multiplexed
IN
A1
address/data bus, nMUX tied Low, A1 is left open,
and ALE is tied to the Address Latch Enable signal.
A2/ALE
IN
A1 is connected to an internal pull-up resistor.
I/O
AD0-AD2,
On a non-multiplexed bus, these signals are used as
D3-D7
the lower byte data bus lines. On a multiplexed
address/data bus, AD0-AD2 act as the address lines
(latched by ALE) and as the low data lines. D3-D7
are always used for data only. These signals are
connected to internal pull-up resistors.
D8-D15
I/O
D8-D15 are always used as the higher byte data bus
lines only for 16bit internal RAM access. When the
16bit access is disabled, these signals are always HiZ. Enabling or disabling the 16bit access is
programmable. A data swapper is built in. These
signals are connected to internal pull-up resistors.
nWR/DIR
IN
nWR is for 80xx CPU, nWR is Write signal input.
Active Low.
DIR is for 68xx CPU, DIR is Bus Direction signal
input. (Low: Write, High: Read.)
nRD/nDS
IN
nRD is for 80xx CPU, nRD is Read signal input.
Active Low.
nDS is for 68xx CPU, nDS is Data Strobe signal
input. Active Low.
nRESET
IN
Hardware reset signal. Active Low.
nINTR
OUT
Interrupt signal output. Active Low.
nCS
IN
Chip Select input. Active Low.
nIOCS16
OUT
BUSTMG
IN
This signal is an active Low signal which indicates
accessing 16bit data only by CPU. This signal
becomes active when CPU accesses to data register
only if W16 bit is 1. This signal is same as on ISA
Bus signal, but it’s not OPEN-DRAIN. An external
OPEN-DRAIN Buffer is needed when this signal
connects to the ISA Bus.
Read and Write Bus Access Timing mode selecting
signal. Status of this signal effects CPU Timing.
L: High speed timing mode (only for non-multiplexed
bus)
H: Normal timing mode
This signal is connected to internal pull-up registers.
Page 8
DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
PIN NO
NAME
24
nPulse 1
25
nPulse 2
28
Receive In
29
nTransmit
Enable
21
22
Crystal
Oscillator
8,20,
32,43
6,11,
18,23,
30,41
19,27,
33,35,
38,40
Power
Supply
SYMBOL
I/O
DESCRIPTION
TRANSMISSION MEDIA INTERFACE
nPULSE1
OUT
In Normal Mode, these active low signals carry the
transmit data information, encoded in pulse format as
DIPULSE waveform. In Backplane Mode, the
nPULSE1 signal driver is programmable (push/pull or
nPULSE2
I/O
open-drain), while the nPULSE2 signal provides a
clock with frequency of doubled data rate. nPULSE1
is connected to a weak internal pull-up resistor on
the open/drain driver in backplane mode.
RXIN
IN
This signal carries the receive data information from
the line transceiver.
nTXEN
OUT
Transmission Enable signal. Active polarity is
programmable through the nPULSE2 pin.
nPULSE2 floating before power-up;
nTXEN active low
nPULSE2 grounded before power-up;
nTXEN active high (this option is only available in
Back Plane mode)
XTAL1
IN
An external crystal should be connected to these
pins. Oscillation frequency range is from 10 MHz to
XTAL2
OUT
20 MHz. If an external TTL clock is used instead, it
must be connected to XTAL1 with a 390ohm pull-up
resistor, and XTAL2 should be left floating.
VDD
PWR +3.3 Volt power supply pins.
Ground
VSS
N/C
N/C
SMSC COM20022I 3.3V Rev.C
PWR
Ground pins.
Non-connection
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DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Power On
Reconfigure
Timer has
Timed Out
Send
Reconfigure
Burst
Read Node ID
Write ID to
RAM Buffer
1
Set NID=ID
Y
Start
Reconfiguration
Timer (210 mS)*
Y
N
N
Invitation
to Transmit to
this ID?
Y
TA?
Transmit
NAK
Y
N
Free Buffer
Enquiry to
this ID?
Y
Y
RI?
Transmit
ACK
Broadcast?
Y
Send
Packet
No
Activity
for 18.7
us?
N
Y
N
N
Y
Y
ACK?
Y
Set NID=ID
Start Timer:
T=(255-ID)
x 36.5 us
Y
Activity
On Line?
Pass the
Token
Set TA
N
N
Broadcast
Enabled?
DID
=ID?
N
Y
N
Write Buffer
with Packet
1
N
No
Activity
for 18.7
us?
Y
N
Set TA
NAK?
Increment
NID
Y
Set TMA
No
Activity
for 18.7
us?
N
N
No Activity
for 20.5
uS?
Y
DID
=0?
Y
ACK?
Y
Was Packet
Broadcast?
N
Write SID
to Buffer
Transmit
Free Buffer
Enquiry
N
N
SOH?
N
RI?
Y
N
CRC
OK?
N
N
T=0?
Y
Y
LENGTH
OK?
N
Y
DID
=0?
- ID refers to the identification number of the ID assigned to this node.
- NID refers to the next identification number that receives the token
Y
Set RI
N
after this ID passes it.
- SID refers to the source identification.
- DID refers to the destination identification.
DID
=ID?
N
Y
- SOH refers to the start of header character; preceeds all data packets.
* Reconfig timer is programmable via setup2 register bits 1, 0.
SEND ACK
Note - All time values are valid for 10Mbps.
Figure 3.1 - COM20022I 3V Operation
Revision 03-08-07
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DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Chapter 4
4.1
Protocol Description
Network Protocol
Communication on the network is based on a token passing protocol. Establishment of the network
configuration and management of the network protocol are handled entirely by the COM20022I 3V's
internal microcoded sequencer. A processor or intelligent peripheral transmits data by simply loading a
data packet and its destination ID into the COM20022I 3V's internal RAM buffer, and issuing a command
to enable the transmitter. When the COM20022I 3V next receives the token, it verifies that the receiving
node is ready by first transmitting a FREE BUFFER ENQUIRY message. If the receiving node transmits
an ACKnowledge message, the data packet is transmitted followed by a 16-bit CRC. If the receiving node
cannot accept the packet (typically its receiver is inhibited), it transmits a Negative AcKnowledge message
and the transmitter passes the token. Once it has been established that the receiving node can accept the
packet and transmission is complete, the receiving node verifies the packet. If the packet is received
successfully, the receiving node transmits an ACKnowledge message (or nothing if it is not received
successfully) allowing the transmitter to set the appropriate status bits to indicate successful or unsuccessful
delivery of the packet. An interrupt mask permits the COM20022I 3V to generate an interrupt to the
processor when selected status bits become true. Figure 3.1 is a flow chart illustrating the internal operation
of the COM20022I 3V connected to a 20 MHz crystal oscillator.
4.2
Data Rates
The COM20022I 3V is capable of supporting data rates from 156.25 Kbps to 10 Mbps. The following
protocol description assumes a 10 Mbps data rate. To attain the faster data rates, the clock frequency may
be doubled or quadrupled by the internal clock multiplier (see next section). For slower data rates, an
internal clock divider scales down the clock frequency. Thus all timeout values are scaled as shown in the
following table:
Example: IDLE LINE Timeout @ 10 Mbps = 20.5 μs. IDLE LINE Timeout for 156.2 Kbps is 20.5 μs * 64 =
1.3 ms
INTERNAL
CLOCK
FREQUENCY
80 MHz
40 MHz
20 MHz
4.2.1
CLOCK
PRESCALER
DATA RATE
TIMEOUT SCALING
FACTOR (MULTIPLY BY)
Div. by 8
Div. by 8
Div. by 8
Div. by 16
Div. by 32
Div. by 64
Div. by 128
10 Mbps
5 Mbps
2.5 Mbps
1.25 Mbps
625 Kbps
312.5 Kbps
156.25 Kbps
1
2
4
8
16
32
64
Selecting Clock Frequencies Above 2.5 Mbps
To realize a 10 Mbps network, an external 80 MHz clock must be input. However, since 80 MHz is the
frequency of FM radio band, it is not practical for use for noise emission reasons. Therefore, higher
frequency clocks are generated from the 20 MHz crystal as selected through two bits in the Setup2
register, CKUP[1,0] as shown below. The selected clock is supplied to the ARCNET controller.
SMSC COM20022I 3.3V Rev.C
Page 11
DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
CKUP1
0
0
1
1
CKUP0
0
1
0
1
CLOCK FREQUENCY (DATA RATE)
20 MHz (Up to 2.5Mbps) Default (Bypass)
40 MHz (Up to 5Mbps)
Reserved
80 MHz (Only 10Mbps)
This clock multiplier is powered-down (bypassed) on default. After changing the CKUP1 and CKUP0 bits,
the ARCNET core operation is stopped and the internal PLL in the clock generator is awakened and it
starts to generate the 40 MHz or 80 MHz. The lock out time of the internal PLL is 8uSec typically. After
more than 8 μsec (this wait time is defined as 1 msec in this data sheet), it is necessary to write command
data '18H' to the command register to re-start the ARCNET core operation. This clock generator is called
“clock multiplier”.
Changing the CKUP1 and CKUP0 bits must be one time or less after releasing a hardware reset.
The EF bit in the SETUP2 register and the SLOWARB bit in the SETUP1 register must be set when the
data rate is over 5 Mbps.
4.3
Network Reconfiguration
A significant advantage of the COM20022I 3V is its ability to adapt to changes on the network. Whenever
a new node is activated or deactivated, a NETWORK RECONFIGURATION is performed. When a new
COM20022I 3V is turned on (creating a new active node on the network), or if the COM20022I 3V has not
received an INVITATION TO TRANSMIT for 210mS, or if a software reset occurs, the COM20022I 3V
causes a NETWORK RECONFIGURATION by sending a RECONFIGURE BURST consisting of eight
marks and one space repeated 765 times. The purpose of this burst is to terminate all activity on the
network. Since this burst is longer than any other type of transmission, the burst will interfere with the next
INVITATION TO TRANSMIT, destroy the token and keep any other node from assuming control of the
line.
When any COM20022I 3V senses an idle line for greater than 20.5μS, which occurs only when the token
Is lost, each COM20022I 3V starts an internal timeout equal to 36.5μs times the quantity 255 minus its
own ID. The COM20022I 3V starts network reconfiguration by sending an invitation to transmit first to itself
and then to all other nodes by decrementing the destination Node ID. If the timeout expires with no line
activity, the COM20022I 3V starts sending INVITATION TO TRANSMIT with the Destination ID (DID)
equal to the currently stored NID. Within a given network, only one COM20022I 3V will timeout (the one
with the highest ID number). After sending the INVITATION TO TRANSMIT, the COM20022I 3V waits for
activity on the line. If there is no activity for 18.7μS, the COM20022I 3V increments the NID value and
transmits another INVITATION TO TRANSMIT using the NID equal to the DID. If activity appears before
the 18.7μS timeout expires, the COM20022I 3V releases control of the line. During NETWORK
RECONFIGURATION, INVITATIONS TO TRANSMIT are sent to all NIDs (1-255).
Each COM20022I 3V on the network will finally have saved a NID value equal to the ID of the COM20022I
3V that it released control to. At this point, control is passed directly from one node to the next with no
wasted INVITATIONS TO TRANSMIT being sent to ID's not on the network, until the next NETWORK
RECONFIGURATION occurs. When a node is powered off, the previous node attempts to pass the token
to it by issuing an INVITATION TO TRANSMIT. Since this node does not respond, the previous node
times out and transmits another INVITATION TO TRANSMIT to an incremented ID and eventually a
response will be received.
The NETWORK RECONFIGURATION time depends on the number of nodes in the network, the
propagation delay between nodes, and the highest ID number on the network, but is typically within the
range of 6 to 15.3 mS.
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
4.4
Broadcast Messages
Broadcasting gives a particular node the ability to transmit a data packet to all nodes on the network
simultaneously. ID zero is reserved for this feature and no node on the network can be assigned ID zero.
To broadcast a message, the transmitting node's processor simply loads the RAM buffer with the data
packet and sets the DID equal to zero. Figure 5.3 illustrates the position of each byte in the packet with
the DID residing at address 0X01 or 1 Hex of the current page selected in the "Enable Transmit from Page
fnn" command. Each individual node has the ability to ignore broadcast messages by setting the most
significant bit of the "Enable Receive to Page fnn" command (see Table 6.7) to a logic "0".
4.5
Extended Timeout Function
There are three timeouts associated with the COM20022I 3V operation. The values of these timeouts are
controlled by bits 3 and 4 of the Configuration Register and bit 5 of the Setup 1 Register.
4.5.1
Response Time
The Response Time determines the maximum propagation delay allowed between any two nodes, and
should be chosen to be larger than the round trip propagation delay between the two furthest nodes on
the network plus the maximum turn around time (the time it takes a particular COM20022I 3V to start
sending a message in response to a received message) which is approximately 3.2 μS. The round trip
propagation delay is a function of the transmission media and network topology. For a typical system
using RG62 coax in a baseband system, a one way cable propagation delay of 7.75 μS translates to a
distance of about 1 mile. The flow chart in Figure 3.1 uses a value of 18.7 μS (7.75 + 7.75 + 3.2) to
determine if any node will respond.
4.5.2
Idle Time
The Idle Time is associated with a NETWORK RECONFIGURATION. Figure 3.1 illustrates that during a
NETWORK RECONFIGURATION one node will continually transmit INVITATIONS TO TRANSMIT until it
encounters an active node. All other nodes on the network must distinguish between this operation and an
entirely idle line. During NETWORK RECONFIGURATION, activity will appear on the line every 20.5 μS.
This 20.5 μS is equal to the Response Time of 18.7 μS plus the time it takes the COM20022I 3V to start
retransmitting another message (usually another INVITATION TO TRANSMIT).
4.5.3
Reconfiguration Time
If any node does not receive the token within the Reconfiguration Time, the node will initiate a NETWORK
RECONFIGURATION. The ET2 and ET1 bits of the Configuration Register allow the network to operate
over longer distances than the 1 mile stated earlier. The logic levels on these bits control the maximum
distances over which the COM20022I 3V can operate by controlling the three timeout values described
above. For proper network operation, all COM20022I 3V's connected to the same network must have the
same Response Time, Idle Time, and Reconfiguration Time.
4.6
Line Protocol
The ARCNET line protocol is considered isochronous because each byte is preceded by a start interval
and ended with a stop interval. Unlike asynchronous protocols, there is a constant amount of time
separating each data byte. On a 10 Mbps network, each byte takes exactly 11 clock intervals of 100ns
each. As a result, one byte is transmitted every 1.1 uS and the time to transmit a message can be
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precisely determined. The line idles in a spacing (logic "0") condition. A logic "0" is defined as no line
activity and a logic "1" is defined as a negative pulse of 50nS 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:
4.6.1
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:
ƒ
ƒ
ƒ
An ALERT BURST
An EOT (End Of Transmission: ASCII code 04H)
Two (repeated) DID (Destination ID) characters
ALERT BURST
4.6.2
EOT
DID
DID
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:
ƒ
ƒ
ƒ
An ALERT BURST
An ENQ (ENQuiry: ASCII code 85H)
Two (repeated) DID (Destination ID) characters
ALERT BURST
4.6.3
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:
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
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)
16
15
2
Two CRC (Cyclic Redundancy Check) characters. The CRC polynomial used is: X + X + X + 1.
ALERT
BURST
Revision 03-08-07
SOH
SID
DID
DID
COUNT
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DATASHEET
data
data
CRC
CRC
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
4.6.4
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:
ƒ
ƒ
An ALERT BURST
An ACK (ACKnowledgement--ASCII code 86H) character
ALERT BURST
4.6.5
ACK
Negative Acknowledgements
A Negative Acknowledgement is used as a negative response to FREE BUFFER ENQUIRIES and is sent
by the following sequence:
ƒ
ƒ
An ALERT BURST
A NAK (Negative Acknowledgement--ASCII code 15H) character
ALERT BURST
SMSC COM20022I 3.3V Rev.C
NAK
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Datasheet
Chapter 5
5.1
System Description
Microcontroller Interface
The top halves of Figure 5.1 and Figure 5.2 illustrate typical COM20022I 3V interfaces to the
microcontrollers. The interfaces consist of a 8-bit data bus, an address bus and a control bus. In order to
support a wide range of microcontrollers without requiring glue logic and without increasing the number of
pins, the COM20022I 3V automatically detects and adapts to the type of microcontroller being used. Upon
hardware reset, the COM20022I 3V first determines whether the read and write control signals are
separate READ and WRITE signals (like the 80XX) or DIRECTION and DATA STROBE (like the 68XX).
To determine the type of control signals, the device requires the software to execute at least one write
access to external memory before attempting to access the COM20022I 3V. The device defaults to 80XXlike signals. Once the type of control signals are determined, the COM20022I 3V remains in this interface
mode until the next hardware reset occurs. The second determination the COM20022I 3V makes is
whether the bus is multiplexed or non-multiplexed. To determine the type of bus, the device requires the
software to write to an odd memory location followed by a read from an odd location before attempting to
access the COM20022I 3V. The signal on the A0 pin during the odd location access tells the COM20022I
3V the type of bus. Since multiplexed operation requires A0 to be active low, activity on the A0 line tells
the COM20022I 3V that the bus is non-multiplexed. The device defaults to multiplexed operation. Both
determinations may be made simultaneously by performing a WRITE followed by a READ operation to an
odd location within the COM20022I 3V Address space 20022 registers. Once the type of bus is
determined, the COM20022I 3V remains in this interface mode until hardware reset occurs.
Whenever nCS and nRD are activated, the preset determinations are assumed as final and will not be
changed until hardware reset. Refer to Description of Pin Functions section for details on the related
signals. All accesses to the internal RAM and the internal registers are controlled by the COM20022I 3V.
The internal RAM is accessed via a pointer-based scheme (refer to the Sequential Access Memory
section), and the internal registers are accessed via direct addressing. Many peripherals are not fast
enough to take advantage of high-speed microcontrollers. Since microcontrollers do not typically have
READY inputs, standard peripherals cannot extend cycles to extend the access time. The access time of
the COM20022I 3V, on the other hand, is so fast that it does not need to limit the speed of the
microcontroller. The COM20022I 3V is designed to be flexible so that it is independent of the
microcontroller speed.
The COM20022I 3V provides for no wait state arbitration via direct addressing to its internal registers and
a pointer based addressing scheme to access its internal RAM. The pointer may be used in autoincrement mode for typical sequential buffer emptying or loading, or it can be taken out of auto-increment
mode to perform random accesses to the RAM. The data within the RAM is accessed through the data
register. Data being read is prefetched from memory and placed into the data register for the
microcontroller to read. It is important to notice that only by writing a new address pointer (writing to an
address pointer low), one obtains the contents of COM20022I 3V internal RAM. Performing only read from
the Data Register does not load new data from the internal RAM. During a write operation, the data is
stored in the data register and then written into memory. Whenever the pointer is loaded for reads with a
new value, data is immediately prefetched to prepare for the first read operation.
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
XTAL1
COM20022
XTAL2
AD0-AD7
AD0-AD2, D3-D7
ALE
A2/BALE
A15
nCS
RXIN
nRESET
RESET
nRD
nRD/nDS
nWR
nINT1
nWR/DIR
nINTR
nTXEN
75176B or
Equiv.
nPULSE1
nPULSE2
GND
Differential Driver
Configuration
8051
A0/nMUX XTAL1
27 pF
* Media Interface
may be replaced
with Figure A, B or C.
XTAL2
27 pF
20 MHz
XTAL
+5V
RXIN
+5V
2
6
RXIN
Receiver
HFD3212-002
7
100 Ohm
TXEN
Transmitter
3 HFE4211-014
nPULSE1
nPULSE1
nPULSE2
+5V
2
6
7
GND
2 Fiber Interface
(ST Connectors)
BACKPLANE CONFIGURATION
NOTE: COM20022 must be in backplane mode
FIGURE B
FIGURE A
3V.
Figure 5.1 - Multiplexed, 8051 - Like Bus Interface with RS-485 Interface
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Datasheet
XTAL1
COM20022
XTAL2
D0-D7
D0-D7
A0
A0/nMUX
A1
A1
A2
A2/BALE
A7
nCS
RXIN
nPULSE1
nRES
nRESET
nIOS
nRD/nDS
R/nW
nWR/nDIR
nIRQ1
75176B or
Equiv.
TXEN
nPULSE2
GND
nINTR
Differential Driver
Configuration
6801
XTAL1
27 pF
* Media Interface
may be replaced
with Figure A, B or C.
XTAL2
27 pF
20MHz
XTAL
+5V
HYC9068 or
HYC9088
10
uF
0.47
uF
6
RXIN
RXIN
+
12
nTXEN
N/C
11
nPULSE1
nPULSE1
nPULSE2
nPULSE2
GND
17, 19,
4, 13, 14
5.6K
1/2W
5.6K
1/2W
0.01 uF
1KV
3
0.47
uF
+ 10
uF
-5V
Traditional Hybrid
Configuration
*Valid for 2.5 Mbps only.
FIGURE C
Figure 5.2 - Non-Multiplexed, 6801-Like Bus Interface with RS-485 Interface
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
5.1.1
Selection of 8/16-Bit Access
The interface to the internal RAM is software selectable as either 8 or 16-bit. This feature is new to the
COM20022I 3V. The D15-D8 pins are the upper-byte data bus pins. The nIOCS16 pin is the 16-bit I/O
access enable output pin. This pin is active low for a 16-bit RAM access by the CPU.
The 16-bit access mode is enabled and disabled through the W16 bit located in the Bus Control Register
at bit 7. The SWAP bit is used to swap the upper and lower data bytes in 16-bit mode, as shown in the
table below. The SWAP bit is located at bit 0 of Address Low Pointer. This location is same as the A0 bit;
when 16 bit access is enabled (W16 =1), the A0 bit becomes the SWAP bit.
DETECTED HOST I/F MODE
Intel 80xx Mode
(RD,WR Mode)
Motorola 68xx Mode
(DIR, DS Mode)
Note:
SWAP BIT (NOTE)
0
1
0
1
D15-D8 PINS
Odd
Even
Even
Odd
D7-D0 PINS
Even
Odd
Odd
Even
The SWAP bit is undefined after a hardware reset
As shown on the table above, even address data is to/from D7-D0 pins and odd address data is to/from
D15-D8 pins when detected host interface mode is Intel 80xx mode and the SWAP bit is not set. The odd
address data is to/from the D7-D0 pins and the even address data is to/from D15-D8 pins when detected
host interface mode is Motorola 68xx mode and the SWAP bit is not set.
When disabling 16-bit access, the D15-D8 pins are always Hi-Z. The D15-D8 pins are Hi-Z when enabling
16-bit access except for internal RAM access.
W16 bit and SWAP bit influence DATA register access only.
5.1.2
High Speed CPU Bus Timing Support
High speed CPU bus support was added to the COM20022I 3V. The reasoning behind this is as follows:
With the Host interface in Non-multiplexed Bus mode, I/O address and Chip Select signals must be stable
before the read signal is active and remain after the read signal is inactive. But the High Speed CPU bus
timing doesn't adhere to these timings. For example, a RISC type single chip microcontroller (like the
HITACHI SH-1 series) changes I/O address at the same time as the read signal. Therefore, several
external logic ICs would be required to connect to this microcontroller.
In addition, the Diagnostic Status (DIAG) register is cleared automatically by reading itself. The internal
DIAG register read signal is generated by decoding the Address (A2-A0), Chip Select (nCS) and Read
(nRD) signals. The decoder will generate a noise spike at the above tight timing. The DIAG register is
cleared by the spike signal without reading itself. This is unexpected operation. Reading the internal RAM
and Next Id Register have the same mechanism as reading the DIAG register.
Therefore, the address decode and host interface mode blocks were modified to fit the above CPU
interface to support high speed CPU bus timing. In Intel CPU mode (nRD, nWR mode), 3 bit I/O address
(A2-A0) and Chip Select (nCS) are sampled internally by Flip-Flops on the falling edge of the internal
delayed nRD signal. The internal real read signal is the more delayed nRD signal. But the rising edge of
nRD doesn't delay. By this modification, the internal real address and Chip Select are stable while the
internal real read signal is active. Refer to Figure 5.3.
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Datasheet
VALID
A2-A0, nCS
nRD
Delayed nRD
(nRD1)
Sampled A2-A0, nCS
VALID
More delayed nRD
(nRD2)
Figure 5.3 - High Speed CPU Bus Timing – Intel CPU Mode
The I/O address and Chip Select signals, which are supplied to the data output logic, are not sampled.
Also, the nRD signal is not delayed, because the above sampling and delaying paths decrease the data
access time of the read cycle.
The above sampling and delaying signals are supplied to the Read Pulse Generation logic which
generates the clearing pulse for the Diagnostic register and generates the starting pulse of the RAM
Arbitration. Typical delay time between nRD and nRD1 is around 15nS and between nRD1 and nRD2 is
around 10nS.
Longer pulse widths are needed due to these delays on nRD signal. However, the CPU can insert some
wait cycles to extend the width without any impact on performance.
The BUSTMG pin is used to support this function. It is used to Enable/Disable the High Speed CPU Read
and Write function. It is defined as: BUSTMG = 0, the High Speed CPU Read and Write operations are
enabled; BUSTMG = 1, the High Speed CPU Read and Write operations are disabled if the RBUSTMG bit
is 0. If BUSTMG = 1 and RBUSTMG = 1, High Speed CPU Read operations are enabled (see definition of
RBUSTMG bit below).
The RBUSTMG bit was added to Disable/Enable the High Speed CPU Read function. It is defined as:
RBUSTMG=0, Disabled (Default); RBUSTMG=1, Enabled.
In the MOTOROLA CPU mode (DIR, nDS mode), the same modifications apply.
BUSTMG PIN
0
1
1
Revision 03-08-07
RBUSTMG BIT
X
0
1
BUS TIMING MODE
High Speed CPU Read and Write
Normal Speed CPU Read and Write
High Speed CPU Read and Normal Speed CPU Write
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
5.2
Transmission Media Interface
The bottom halves of Figure 5.1 and Figure 5.2 illustrate the COM20022I 3V interface to the transmission
media used to connect the node to the network. Table 5.1 lists different types of cable which are suitable
for ARCNET applications.1 The user may interface to the cable of choice in one of three ways:
5.2.1
Traditional Hybrid Interface
The Traditional Hybrid Interface is that which is used with previous ARCNET devices. The Hybrid
Interface is recommended if the node is to be placed in a network with other Hybrid-Interfaced nodes. The
Traditional Hybrid Interface is for use with nodes operating at 2.5 Mbps only. The transformer coupling of
the Hybrid offers isolation for the safety of the system and offers high Common Mode Rejection. The
Traditional Hybrid Interface uses circuits like SMSC's HYC9068 or HYC9088 to transfer the pulse-encoded
data between the cable and the COM20022I 3V. The COM20022I 3V transmits a logic "1" by generating
two 100nS non-overlapping negative pulses, nPULSE1 and nPULSE2. Lack of pulses indicates a logic
"0". The nPULSE1 and nPULSE2 signals are sent to the Hybrid, which creates a 200nS dipulse signal on
the media. A logic "0" is transmitted by the absence of the dipulse. During reception, the 200nS dipulse
appearing on the media is coupled through the RF transformer of the LAN Driver, which produces a
positive pulse at the RXIN pin of the COM20022I 3V. The pulse on the RXIN pin represents a logic "1".
Lack of pulse represents a logic "0". Typically, RXIN pulses occur at multiples of 400nS. The COM20022I
3V can tolerate distortion of plus or minus 100nS and still correctly capture and convert the RXIN pulses to
NRZ format. Figure 5.5 illustrates the events which occur in transmission or reception of data consisting of
1, 1, 0.
5.2.2
Backplane Configuration
The Backplane Open Drain Configuration is recommended for cost-sensitive, short-distance applications
like backplanes and instrumentation. This mode is advantageous because it saves components, cost, and
power.
Since the Backplane Configuration encodes data differently than the traditional Hybrid Configuration,
nodes utilizing the Backplane Configuration cannot communicate directly with nodes utilizing the
Traditional Hybrid Configuration. The Backplane Configuration does not isolate the node from the media
nor protects it from Common Mode noise, but Common Mode Noise is less of a problem in short
distances.
The COM20022I 3V supplies a programmable output driver for Backplane Mode operation. A push/pull or
open drain driver can be selected by programming the P1MODE bit of the Setup 1 Register (see register
descriptions for details). The COM20022I 3V defaults to an open drain output.
The Backplane Configuration provides for direct connection between the COM20022I 3V and the media.
Only one pull-up resistor (in open drain configuration of the output driver) is required somewhere on the
media (not on each individual node). The nPULSE1 signal, in this mode, is an open drain or push/pull
driver and is used to directly drive the media. It issues a 200nS negative pulse to transmit a logic "1". Note
that when used in the open-drain mode, the COM20022I 3V does not have a fail/safe input on the RXIN
pin. The nPULSE1 signal actually contains a weak pull-up resistor. This pull-up should not take the place
of the resistor required on the media for open drain mode.
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Datasheet
RT
RT
+VCC
+VCC
+VCC
RBIAS
RBIAS
75176B or
Equiv.
COM20022I 3V
COM20022I 3V
RBIAS
COM20022I 3V
Figure 5.4 - COM20022I 3V Network Using RS-485 Differential Transceivers
ONLY)
1
1
20MHZ
CLOCK
(FOR REF.
0
100ns
nPULSE1
100ns
nPULSE2
200ns
DIPULSE
400ns
RXIN
Figure 5.5 - Dipluse Waveform for Data of 1-1-0
In typical applications, the serial backplane is terminated at both ends and a bias is provided by the
external pull-up resistor.
The RXIN signal is directly connected to the cable via an internal Schmitt trigger. A negative pulse on this
input indicates a logic "1". Lack of pulse indicates a logic "0". For typical single-ended backplane
applications, RXIN is connected to nPULSE1 to make the serial backplane data line. A ground line (from
the coax or twisted pair) should run in parallel with the signal. For applications requiring different treatment
of the receive signal (like filtering or squelching), nPULSE1 and RXIN remain as independent pins.
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
External differential drivers/receivers for increased range and common mode noise rejection, for example,
would require the signals to be independent of one another. When the device is in Backplane Mode, the
clock provided by the nPULSE2 signal may be used for encoding the data into a different encoding
scheme or other synchronous operations needed on the serial data stream.
5.2.3
Differential Driver Configuration
The Differential Driver Configuration is a special case of the Backplane Mode. It is a dc coupled
configuration recommended for applications like car-area networks or other cost-sensitive applications
which do not require direct compatibility with existing ARCNET nodes and do not require isolation.
The Differential Driver Configuration cannot communicate directly with nodes utilizing the Traditional
Hybrid Configuration. Like the Backplane Configuration, the Differential Driver Configuration does not
isolate the node from the media.
The Differential Driver interface includes a RS485 Driver/Receiver to transfer the data between the cable
and the COM20022I 3V. The nPULSE1 signal transmits the data, provided the Transmit Enable signal is
active. The nPULSE1 signal issues a 200nS (at 2.5Mbps) negative pulse to transmit a logic "1". Lack of
pulse indicates a logic "0". The RXIN signal receives the data, the transmitter portion of the COM20022I
3V is disabled during reset and the nPULSE1, nPULSE2 and nTXEN pins are inactive.
5.2.4
Programmable TXEN Polarity
To accommodate transceivers with active high ENABLE pins, the COM20022I 3V contains a
programmable TXEN output. To program the TXEN pin for an active high pulse, the nPULSE2 pin should
be connected to ground. To retain the normal active low polarity, nPULSE2 should be left open. The
polarity determination is made at power on reset and is valid only for Backplane Mode operation. The
nPULSE2 pin should remain grounded at all times if an active high polarity is desired.
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Datasheet
Figure 5.6 - Internal Block Diagram
Table 5.1 - Typical Media
NOMINAL
IMPEDANCE
ATTENUATION PER
1000 FT. AT 5 MHZ
RG-62 Belden #86262
93Ω
5.5dB
RG-59/U Belden #89108
75Ω
7.0dB
RG-11/U Belden #89108
75Ω
5.5dB
IBM Type 1 (Note 5.1)
Belden #89688
IBM Type 3 (Note 5.1)
Telephone Twisted Pair Belden
#1155A
COMCODE 26 AWG Twisted Pair
Part #105-064-703
150Ω
7.0dB
100Ω
17.9dB
105Ω
16.0dB
CABLE TYPE
Note 5.1
Non-plenum-rated cables of this type are also available.
Revision 03-08-07
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DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Chapter 6
6.1
Functional Description
Microsequencer
The COM20022I 3V contains an internal microsequencer which performs all of the control operations
necessary to carry out the ARCNET protocol. It consists of a clock generator, a 544 x 8 ROM, a program
counter, two instruction registers, an instruction decoder, a no-op generator, jump logic, and
reconfiguration logic.
The COM20022I 3V derives a 20 MHz and a 10 MHz clock from the output clock of the Clock Multiplier.
These clocks provide the rate at which the instructions are executed within the COM20022I 3V. The 20
MHz clock is the rate at which the program counter operates, while the 10 MHz clock is the rate at which
the instructions are executed. The microprogram is stored in the ROM and the instructions are fetched
and then placed into the instruction registers. One register holds the opcode, while the other holds the
immediate data. Once the instruction is fetched, it is decoded by the internal instruction decoder, at which
point the COM20022I 3V proceeds to execute the instruction. When a no-op instruction is encountered,
the microsequencer enters a timed loop and the program counter is temporarily stopped until the loop is
complete. When a jump instruction is encountered, the program counter is loaded with the jump address
from the ROM. The COM20022I 3V contains an internal reconfiguration timer which interrupts the
microsequencer if it has timed out. At this point the program counter is cleared and the MYRECON bit of
the Diagnostic Status Register is set.
Table 6.1 - Read Register Summary
READ
REGISTER
STATUS
MSB
RI/TRI
DIAG.
STATUS
ADDRESS
PTR HIGH
ADDRESS
PTR LOW
DATA
LSB
TA/
TTA
X
ADDR
00
A9
A8
02
A2
A1
A0/ SWAP
03
D3
D2
D1
D0
04
X
X
SUB-AD2
SUB-AD1
SUB-AD0
05
X/RI
X/TA
POR
TEST
RECON
TMA
MYRECON
DUPID
RCV-ACT
TOKEN
EXC-NAK
TENTID
NEW
NEXTID
RD-DATA
AUTO-INC
X
X
X
A10
A7
A6
A5
A4
A3
D7
D6
D5
D4
X
01
*See Table 6.2
SUB ADR
(R/W)
(R/W)
(Note 6.1)
(Note 6.1)
CONFIGURATION
TENTID
NODE ID
SETUP1
RESET
CCHEN
TXEN
ET1
ET2
BACKPLANE
SUB-AD1
SUB-AD0
06
TID7
NID7
P1 MODE
TID5
NID5
X
TID4
NID4
RCV- ALL
TID3
NID3
CKP3
TID2
NID2
CKP2
TID1
NID1
CKP1
TID0
NID0
SLOWARB
07-0
07-1
07-2
NEXT ID
NXT ID7
TID6
NID6
FOUR
NAKS
NXT ID6
NXT ID5
NXT ID4
NXT ID3
NXT ID1
NXT ID0
07-3
SETUP2
RBUSTMG
X
CKUP1
CKUP0
EF
NXT
ID2
NO-SYNC
RCN-TM1
RCM-TM2
07-4
SMSC COM20022I 3.3V Rev.C
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
READ
REGISTER
BUS
CONTROL
MSB
W16
Note 6.1
X
X
X
X
X
LSB
X
X
ADDR
07-5
These bits can be written and read. For more information see Appendix C
Table 6.2 - Data Register at 16 Bit Access
REGISTER
BIT
15
BIT
14
BIT
13
BIT
12
BIT
11
BIT
10
BIT
9
BIT
8
BIT
7
BIT
6
BIT
5
BIT
4
BIT
3
BIT
2
BIT
1
BIT
0
ADDR
DATA
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
04
Table 6.3 - Write Register Summary
WRITE
ADDR
00
MSB
RI/TR1
0
0
0
EXCNAK
RECON
NEW
NEXTID
C5
0
C4
0
C3
0
C2
A10
C1
A9
A7
C6
AUTOINC
A6
LSB
TA/
TTA
C0
A8
01
02
C7
RD-DATA
03
A5
A4
A3
A2
A1
A0/ SWAP
04
D7
D6
D5
D4
D3
D2
D1
D0
REGISTER
INTERRUPT
MASK
COMMAND
ADDRESS
PTR HIGH
ADDRESS
PTR LOW
DATA
*See Table 6.4
05
(R/W)
(R/W)
(Note 6.2)
(Note 6.2)
0
0
0
SUB-AD2
SUB- AD1
06
RESET
CCHEN
TXEN
ET1
ET2
TID6
NID6
FOUR
NAKS
0
0
TID5
NID5
0
TID3
NID3
CKP3
SUBAD1
TID1
NID1
CKP1
SLOW-ARB
0
CKUP1
TID4
NID4
RCVALL
0
CKUP0
BACKPLANE
TID2
NID2
CKP2
07-0
07-1
07-2
TID7
NID7
P1-MODE
07-3
07-4
0
RBUSTMG
0
0
0
0
0
NOSYNC
0
0
RCNTM1
0
0
RCNTM0
0
07-5
W16
0
EF
SUBADR
SUBAD0
SUBAD0
TID0
NID0
CONFIGURATION
TENTID
NODEID
SETUP1
TEST
SETUP2
BUS
CONTROL
Note 6.2 These bits can be written and read. For more information see Appendix C
Table 6.4 - Data Register at 16 Bit Address
REGISTER
BIT
15
BIT
14
BIT
13
BIT
12
BIT
11
BIT
10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
ADDR
DATA
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
04
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
6.2
Internal Registers
The COM20022I 3V contains 16 internal registers. Table 6.1 and Table 6.3 illustrate the COM20022I 3V
register map. All undefined bits are read as undefined and must be written as logic "0".
6.2.1
Interrupt Mask Register (IMR)
The COM20022I 3V is capable of generating an interrupt signal when certain status bits become true. A
write to the IMR specifies which status bits will be enabled to generate an interrupt. The bit positions in the
IMR are in the same position as their corresponding status bits in the Status Register and Diagnostic
Status Register. A logic "1" in a particular position enables the corresponding interrupt. The Status bits
capable of generating an interrupt include the Receiver Inhibited bit, New Next ID bit, Excessive NAK bit,
Reconfiguration Timer bit, and Transmitter Available bit. No other Status or Diagnostic Status bits can
generate an interrupt.
The six maskable status bits are ANDed with their respective mask bits, and the results are ORed to
produce the interrupt signal. An RI or TA interrupt is masked when the corresponding mask bit is reset to
logic "0", but will reappear when the corresponding mask bit is set to logic "1" again, unless the interrupt
status condition has been cleared by this time. A RECON interrupt is cleared when the "Clear Flags"
command is issued. An EXCNAK interrupt is cleared when the "POR Clear Flags" command is issued. A
New Next ID interrupt is cleared by reading the Next ID Register. The Interrupt Mask Register defaults to
the value 0000 0000 upon hardware reset.
6.2.2
Data Register
This read/write 8-bit register is used as the channel through which the data to and from the RAM passes.
The data is placed in or retrieved from the address location presently specified by the address pointer.
The contents of the Data Register are undefined upon hardware reset. In case of READ operation, the
Data Register is loaded with the contents of COM20022I 3V Internal Memory upon writing Address Pointer
low only once.
The SWAP bit is used to swap the upper and lower data byte. The SWAP bit is located at bit 0 of
ADDRESS PTR_LOW register. When 16 bit access is enabled, (W16=1), A0 becomes the SWAP bit.
6.2.3
Tentative ID Register
The Tentative ID Register is a read/write 8-bit register accessed when the Sub Address Bits are set up
accordingly (please refer to the Configuration Register and SUB ADR Register). The Tentative ID Register
can be used while the node is on-line to build a network map of those nodes existing on the network. It
minimizes the need for operator interaction with the network. The node determines the existence of other
nodes by placing a Node ID value in the Tentative ID Register and waiting to see if the Tentative ID bit of
the Diagnostic Status Register gets set. The network map developed by this method is only valid for a
short period of time, since nodes may join or depart from the network at any time. When using the
Tentative ID feature, a node cannot detect the existence of the next logical node to which it passes the
token. The Next ID Register will hold the ID value of that node. The Tentative ID Register defaults to the
value 0000 0000 upon hardware reset only.
SMSC COM20022I 3.3V Rev.C
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
6.2.4
Node ID Register
The Node ID Register is a read/write 8-bit register accessed when the Sub Address Bits are set up
accordingly (please refer to the Configuration Register and SUB ADR Register). The Node ID Register
contains the unique value which identifies this particular node. Each node on the network must have a
unique Node ID value at all times. The Duplicate ID bit of the Diagnostic Status Register helps the user
find a unique Node ID. Refer to the Initialization Sequence section for further detail on the use of the
DUPID bit. The core of the COM20022I 3V does not wake up until a Node ID other than zero is written
into the Node ID Register. During this time, no microcode is executed, no tokens are passed by this node,
and no reconfigurations are caused by this node. Once a non-zero NodeID is placed into the Node ID
Register, the core wakes up but will not join the network until the TXEN bit of the Configuration Register is
set. While the Transmitter is disabled, the Receiver portion of the device is still functional and will provide
the user with useful information about the network. The Node ID Register defaults to the value 0000 0000
upon hardware reset only.
6.2.5
Next ID Register
The Next ID Register is an 8-bit, read-only register, accessed when the sub-address bits are set up
accordingly (please refer to the Configuration Register and SUB ADR Register). The Next ID Register
holds the value of the Node ID to which the COM20022I 3V will pass the token. When used in conjunction
with the Tentative ID Register, the Next ID Register can provide a complete network map. The Next ID
Register is updated each time a node enters/leaves the network or when a network reconfiguration occurs.
Each time the microsequencer updates the Next ID Register, a New Next ID interrupt is generated. This bit
is cleared by reading the Next ID Register. Default value is 0000 0000 upon hardware or software reset.
6.2.6
Status Register
The COM20022I 3V Status Register is an 8-bit read-only register. All of the bits, except for bits 5 and 6,
are software compatible with previous SMSC ARCNET devices. In previous SMSC ARCNET devices the
Extended Timeout status was provided in bits 5 and 6 of the Status Register. In the COM20022I 3V, the
COM20020, the COM90C66, and the COM90C165, COM20020-5, COM20051 and COM20051+ these
bits exist in and are controlled by the Configuration Register. The Status Register contents are defined as
in Table 6.5, but are defined differently during the Command Chaining operation. Please refer to the
Command Chaining section for the definition of the Status Register during Command Chaining operation.
The Status Register defaults to the value 1XX1 0001 upon either hardware or software reset.
6.2.7
Diagnostic Status Register
The Diagnostic Status Register contains seven read-only bits which help the user troubleshoot the network
or node operation. Various combinations of these bits and the TXEN bit of the Configuration Register
represent different situations. All of these bits, except the Excessive NACK bit and the New Next ID bit,
are reset to logic "0" upon reading the Diagnostic Status Register or upon software or hardware reset. The
EXCNAK bit is reset by the "POR Clear Flags" command or upon software or hardware reset. The
Diagnostic Status Register defaults to the value 0000 000X upon either hardware or software reset.
6.2.8
Command Register
Execution of commands are initiated by performing microcontroller writes to this register. Any
combinations of written data other than those listed in Table 6.7 are not permitted and may result in
incorrect chip and/or network operation.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
6.2.9
Address Pointer Registers
These read/write registers are each 8-bits wide and are used for addressing the internal RAM. New pointer
addresses should be written by first writing to the High Register and then writing to the Low Register
because writing to the Low Register loads the address. The contents of the Address Pointer High and Low
Registers are undefined upon hardware reset. Writing to Address Pointer low loads the address.
The SWAP bit (new to the COM20022I 3V) is located at bit 0 of Address Pointer Low register. The SWAP bit
is used to swap the upper and lower data byte. When 16 bit access is enabled, (W16=1), A0 becomes the
SWAP bit.
6.2.10 Configuration Register
The Configuration Register is a read/write register which is used to configure the different modes of the
COM20022I 3V. The Configuration Register defaults to the value 0001 1000 upon hardware reset only.
SUBAD0 and SUBAD1 point to the selection in Register 7.
6.2.11 Sub-Address Register
The sub-address register is new to the COM20022I 3V, previously a reserved register. Bits 2, 1 and 0 are
used to select one of the registers assigned to address 7h. SUBAD1 and SUBAD0 already exist in the
Configuration register on the COM20020B. They are exactly same as those in the Configuration register.
If the SUBAD1 and SUBAD0 bits in the Configuration register are changed, the SUBAD1and SUBAD0 in
the Sub-Address register are also changed. SUBAD2 is a new sub-address bit. It Is used to access the 2
new Set Up registers, SETUP2 and BUS CONTROL. These registers are selected by setting SUBAD2=1.
The SUBAD2 bit is cleared automatically by writing the Configuration register.
Write Bits[7:3] to ‘0’ for proper operation.
6.2.12 Setup 1 Register
The Setup 1 Register is a read/write 8-bit register accessed when the Sub Address Bits are set up
accordingly (see the bit definitions of the Configuration Register). The Setup 1 Register allows the user to
change the network speed (data rate) or the arbitration speed independently, invoke the Receive All
feature and change the nPULSE1 driver type. The data rate may be slowed to 156.25Kbps and/or the
arbitration speed may be slowed by a factor of two. The Setup 1 Register defaults to the value 0000 0000
upon hardware reset only.
6.2.13 Setup 2 Register
The Setup 2 Register is new to the COM20022I 3V. It is an 8-bit read/write register accessed when the
Sub Address Bits SUBAD[2:0] are set up accordingly (see the bit definitions of the Sub Address Register).
This register contains bits for various functions. The CKUP1,0 bits select the clock to be generated from
the 20 MHz crystal. The RBUSTMG bit is used to Disable/Enable Fast Read function for High Speed CPU
bus support. The EF bit is used to enable the new timing for certain functions in the COM20022I 3V (if EF
= 0, the timing is the same as in the COM20020 Rev. B). See Appendix “A”. The NOSYNC bit is used to
enable the NOSYNC function during initialization. If this bit is reset, the line has to be idle for the RAM
initialization sequence to be written. If set, the line does not have to be idle for the initialization sequence
to be written. See Appendix “A”.
The RCNTM[1,0] bits are used to set the time-out period of the recon timer. Programming this timer for
shorter time periods has the benefit of shortened network reconfiguration periods. The time periods shown
SMSC COM20022I 3.3V Rev.C
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
in the table following are limited by a maximum number of nodes in the network. These time-out period
values are for 10Mbps. For other data rates, scale the time-out period time values accordingly; the
maximum node count remains the same.
RCNTM1
0
0
1
1
Note 6.3
RCNTM0
0
1
0
1
TIME-OUT PERIOD
210 mS
52.5 mS
26.25 mS
13.125 mS (Note 6.3)
MAX NODE COUNT
Up to 255 nodes
Up to 64 nodes
Up to 32 nodes
Up to 16 nodes (Note 6.3)
The node ID value 255 must exist in the network for the 13.125 mS time-out to be valid.
6.2.14 Bus Control Register
The W16 bit is used to enable/disable the 16 bit access.
Table 6.5 - Status Register
BIT
BIT NAME
7 Receiver
Inhibited
6,5
4
3
2
1
SYMBOL
DESCRIPTION
RI
This bit, if high, indicates that the receiver is not enabled because
either an "Enable Receive to Page fnn" command was never
issued, or a packet has been deposited into the RAM buffer page
fnn as specified by the last "Enable Receive to Page fnn"
command. No messages will be received until this command is
issued, and once the message has been received, the RI bit is
set, thereby inhibiting the receiver. The RI bit is cleared by
issuing an "Enable Receive to Page fnn" command. This bit,
when set, will cause an interrupt if the corresponding bit of the
Interrupt Mask Register (IMR) is also set. When this bit is set and
another station attempts to send a packet to this station, this
station will send a NAK.
(Reserved)
These bits are undefined.
Power On Reset POR
This bit, if high, indicates that the COM20022I 3V has been reset
by either a software reset, a hardware reset, or writing 00H to the
Node ID Register. The POR bit is cleared by the "Clear Flags"
command.
Test
TEST
This bit is intended for test and diagnostic purposes. It is a logic
"0" under normal operating conditions.
Reconfiguration RECON
This bit, if high, indicates that the Line Idle Timer has timed out
because the RXIN pin was idle for 20.5 S. The RECON bit is
cleared during a "Clear Flags" command. This bit, when set, will
cause an interrupt if the corresponding bit in the IMR is also set.
The interrupt service routine should consist of examining the
MYRECON bit of the Diagnostic Status Register to determine
whether there are consecutive reconfigurations caused by this
node.
TMA
Transmitter
This bit, if high, indicates that the packet transmitted as a result of
an "Enable Transmit from Page fnn" command has been
Message
acknowledged. This bit should only be considered valid after the
Acknowledged
TA bit (bit 0) is set. Broadcast messages are never
acknowledged. The TMA bit is cleared by issuing the "Enable
Transmit from Page fnn" command.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
BIT
BIT NAME
0 Transmitter
Available
SYMBOL
DESCRIPTION
TA
This bit, if high, indicates that the transmitter is available for
transmitting. This bit is set when the last byte of scheduled
packet has been transmitted out, or upon execution of a "Disable
Transmitter" command. The TA bit is cleared by issuing the
"Enable Transmit from Page fnn" command after the node next
receives the token. This bit, when set, will cause an interrupt if
the corresponding bit in the IMR is also set.
Table 6.6 - Diagnostic Status Register
BIT
BIT NAME
7 My
Reconfiguration
6
Duplicate ID
5
Receive
Activity
4
Token Seen
3
Excessive NAK
2
Tentative ID
1
New Next ID
0
(Reserved)
SMSC COM20022I 3.3V Rev.C
SYMBOL
DESCRIPTION
MYThis bit, if high, indicates that a past reconfiguration was caused
by this node. It is set when the Lost Token Timer times out, and
RECON
should be typically read following an interrupt caused by RECON.
Refer to the Improved Diagnostics section for further detail.
DUPID
This bit, if high, indicates that the value in the Node ID Register
matches both Destination ID characters of the token and a
response to this token has occurred. Trailing zero's are also
verified. A logic "1" on this bit indicates a duplicate Node ID, thus
the user should write a new value into the Node ID Register. This
bit is only useful for duplicate ID detection when the device is off
line, that is, when the transmitter is disabled. When the device is
on line this bit will be set every time the device gets the token.
This bit is reset automatically upon reading the Diagnostic Status
Register. Refer to the Improved Diagnostics section for further
detail.
RCVACT This bit, if high, indicates that data activity (logic "1") was
detected on the RXIN pin of the device. Refer to the Improved
Diagnostics section for further detail.
TOKEN
This bit, if high, indicates that a token has been seen on the
network, sent by a node other than this one. Refer to the
Improved Diagnostic section for further detail.
EXCNAK This bit, if high, indicates that either 128 or 4 Negative
Acknowledgements have occurred in response to the Free Buffer
Enquiry. This bit is cleared upon the "POR Clear Flags"
command. Reading the Diagnostic Status Register does not
clear this bit. This bit, when set, will cause an interrupt if the
corresponding bit in the IMR is also set. Refer to the Improved
Diagnostics section for further detail.
TENTID
This bit, if high, indicates that a response to a token whose DID
matches the value in the Tentative ID Register has occurred.
The second DID and the trailing zero's are not checked. Since
each node sees every token passed around the network, this
feature can be used with the device on-line in order to build and
update a network map. Refer to the Improved Diagnostics
section for further detail.
NEW
This bit, if high, indicates that the Next ID Register has been
updated and that a node has either joined or left the network.
NXTID
Reading the Diagnostic Status Register does not clear this bit.
This bit, when set, will cause an interrupt if the corresponding bit
in the IMR is also set. The bit is cleared by reading the Next ID
Register.
This bit is undefined.
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DATASHEET
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Table 6.7 - Command Register
DATA
0000 0000
0000 0001
COMMAND
Clear
Transmit
Interrupt
Disable
Transmitter
0000 0010
Disable
Receiver
b0fn n100
Enable
Receive to
Page fnn
00fn n011
Enable
Transmit from
Page fnn
0000 c101
Define
Configuration
000r p110
Clear Flags
0000 1000
Clear
Receive
Interrupt
Start Internal
Operation
0001 1000
Revision 03-08-07
DESCRIPTION
This command is used only in the Command Chaining
operation. Please refer to the Command Chaining section for
definition of this command.
This command will cancel any pending transmit command
(transmission that has not yet started) and will set the TA
(Transmitter Available) status bit to logic "1" when the
COM20022I 3V next receives the token.
This command will cancel any pending receive command. If the
COM20022I 3V is not yet receiving a packet, the RI (Receiver
Inhibited) bit will be set to logic "1" the next time the token is
received. If packet reception is already underway, reception will
run to its normal conclusion.
This command allows the COM20022I 3V to receive data
packets into RAM buffer page fnn and resets the RI status bit to
logic "0". The values placed in the "nn" bits indicate the page
that the data will be received into (page 0, 1, 2, or 3). If the
value of "f" is a logic "1", an offset of 256 bytes will be added to
that page specified in "nn", allowing a finer resolution of the
buffer. Refer to the Selecting RAM Page Size section for further
detail. If the value of "b" is logic "1", the device will also receive
broadcasts (transmissions to ID zero). The RI status bit is set to
logic "1" upon successful reception of a message.
This command prepares the COM20022I 3V to begin a transmit
sequence from RAM buffer page fnn the next time it receives
the token. The values of the "nn" bits indicate which page to
transmit from (0, 1, 2, or 3). If "f" is logic "1", an offset of 256
bytes is the start of the page specified in "nn", allowing a finer
resolution of the buffer. Refer to the Selecting RAM Page Size
section for further detail. When this command is loaded, the TA
and TMA bits are reset to logic "0". The TA bit is set to logic "1"
upon completion of the transmit sequence. The TMA bit will
have been set by this time if the device has received an ACK
from the destination node. The ACK is strictly hardware level,
sent by the receiving node before its microcontroller is even
aware of message reception. Refer to Figure 3.1 - COM20022I
3V Operation for details of the transmit sequence and its
relation to the TA and TMA status bits.
This command defines the maximum length of packets that may
be handled by the device. If "c" is a logic "1", the device
handles both long and short packets. If "c" is a logic "0", the
device handles only short packets.
This command resets certain status bits of the COM20022I 3V.
A logic "1" on "p" resets the POR status bit and the EXCNAK
Diagnostic status bit. A logic "1" on "r" resets the RECON
status bit.
This command is used only in the Command Chaining
operation. Please refer to the Command Chaining section for
definition of this command.
This command restarts the stopped internal operation after
changing CKUP1 or CKUP0 bit.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Table 6.8 - Address Pointer High Register
BIT
7
BIT NAME
Read Data
SYMBOL
RDDATA
6
Auto Increment
AUTOINC
(Reserved)
(Reserved)
Address 10-8
A10-A8
5-4
3
2-0
DESCRIPTION
This bit tells the COM20022I 3V whether the following
access will be a read or write. A logic "1" prepares the
device for a read, a logic "0" prepares it for a write.
This bit controls whether the address pointer will
increment automatically after DATA register access. A
logic "1" on this bit allows automatic increment of the
pointer after each DATA register access, while a logic "0"
disables this function.
- At 8 bit access mode (W16=0)
AUTOINC=0: The address pointer does not increment
AUTOINC=1: The address pointer increment (+1)
- At 16 bit access mode (W16=1)
AUTOINC=0: The address pointer does not increment
AUTOINC=1: The address pointer increment (+2)
Please refer to the Sequential Access Memory section for
further detail.
These bits are undefined. They must be 0.
This bit must be “0” for normal operation.
These bits hold the upper three address bits which
provide addresses to RAM.
Table 6.9 - Address Pointer Low Register
BIT
7-0
BIT NAME
Address 7-0
SYMBOL
A7-A0
SWAP
DESCRIPTION
These bits hold the lower 8 address bits which provide the
addresses to RAM.
When 16 bit access is enabled, (W16=1), A0 becomes the
SWAP bit. Swap bit is undefined after a hardware reset.
The swap bit must be set before W16 bit is set to “1”. The
swap bit is used to swap the upper and lower data byte.
The swap bit influences CPU cycle. See Table Below.
Detected Host
Interface Mode
Intel 80xx Mode
(RD, WR Mode)
Motorola 68xx Mode
(DIR, DS Mode)
SMSC COM20022I 3.3V Rev.C
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DATASHEET
Swap Bit
0
1
0
1
D15-D8
Pin
Odd
Even
Even
Odd
D7-D0
Pin
Even
Odd
Odd
Even
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Table 6.10 - Sub Address Register
BIT
7-3
2,1,0
BIT NAME
Reserved
Sub Address 2,1,0
SYMBOL
SUBAD
2,1,0
DESCRIPTION
These bits are undefined. They must be 0.
These bits determine which register at address 07 may be
accessed. The combinations are as follows:
SUBAD2 SUBAD1 SUBAD0 Register
0
0
0
Tentative ID \ (Same
0
0
1
Node ID
\ as in
0
1
0
Setup 1
/ Config
0
1
1
Next ID
/ Register)
1
0
0
Setup 2
1
0
1
Bus Control
1
1
0
Reserved
1
1
1
Reserved
SUBAD1 and SUBAD0 are exactly the same as exist in the
Configuration Register. SUBAD2 is cleared automatically by
writing the Configuration Register.
Table 6.11 - Configuration Register
BIT
7
BIT NAME
Reset
SYMBOL
RESET
6
Command
Chaining Enable
CCHEN
5
Transmit Enable
TXEN
Revision 03-08-07
DESCRIPTION
A software reset of the COM20022I 3V is executed by
writing a logic "1" to this bit. A software reset does not
reset the microcontroller interface mode, nor does it affect
the Configuration Register. The only registers that the
software reset affect are the Status Register, the Next ID
Register, and the Diagnostic Status Register. This bit
must be brought back to logic "0" to release the reset.
This bit, if high, enables the Command Chaining operation
of the device. Please refer to the Command Chaining
section for further details. A low level on this bit ensures
software compatibility with previous SMSC ARCNET
devices.
When low, this bit disables transmissions by keeping
nPULSE1, nPULSE2 if in non-Backplane Mode, and
nTXEN pin inactive. When high, it enables the above
signals to be activated during transmissions. This bit
defaults low upon reset. This bit is typically enabled once
the Node ID is determined, and never disabled during
normal operation. Please refer to the Improved
Diagnostics section for details on evaluating network
activity.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
BIT
4,3
2
1,0
BIT NAME
Extended
Timeout 1,2
SYMBOL
ET1, ET2
Backplane
BACKPLANE
Sub Address 1,0
SUBAD 1,0
DESCRIPTION
These bits allow the network to operate over longer
distances than the default maximum 1 mile by controlling
the Response, Idle, and Reconfiguration Times. All nodes
should be configured with the same timeout values for
proper network operation. For the COM20022I 3V with a
20 MHz crystal oscillator, the bit combinations follow:
Reconfig
Response Idle Time
Time
(mS)
ET1
ET2
(μS)
Time (μS)
420
0
0
298.4
328
420
0
1
149.2
164
420
1
0
74.7
82
210
1
1
18.7
20.5
Note: These values are for
10Mbps and RCNTMR[1,0]=00.
Reconfiguration time is changed by the RCNTMR1
and RCNTMR0 bits.
A logic "1" on this bit puts the device into Backplane Mode
signaling which is used for Open Drain and Differential
Driver interfaces.
These bits determine which register at address 07 may be
accessed. The combinations are as follows:
SUBAD1
SUBAD0
0
0
0
1
1
0
1
1
See also the Sub Address Register.
SMSC COM20022I 3.3V Rev.C
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DATASHEET
Register
Tentative ID
Node ID
Setup 1
Next ID
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Table 6.12 - Setup 1 Register
BIT
7
BIT NAME
Pulse1 Mode
SYMBOL
P1MODE
6
Four NACKS
FOUR
NACKS
5
4
Reserved
Receive All
3,2,1 Clock Prescaler
Bits 3,2,1
0
Revision 03-08-07
Slow Arbitration
Select
RCVALL
CKP3,2,1
SLOWARB
DESCRIPTION
This bit determines the type of PULSE1 output driver used
in Backplane Mode. When high, a push/pull output is
used. When low, an open drain output is used. The
default is open drain.
This bit, when set, will cause the EXNACK bit in the
Diagnostic Status Register to set after four NACKs to Free
Buffer Enquiry are detected by the COM20022I 3V. This
bit, when reset, will set the EXNACK bit after 128 NACKs
to Free Buffer Enquiry. The default is 128.
Do not set. It must be 0.
This bit, when set, allows the COM20022I 3V to receive all
valid data packets on the network, regardless of their
destination ID. This mode can be used to implement a
network monitor with the transmitter on- or off-line. Note
that ACKs are only sent for packets received with a
destination ID equal to the COM20022I 3V's programmed
node ID. This feature can be used to put the COM20022I
3V in a 'listen-only' mode, where the transmitter is
disabled and the COM20022I 3V is not passing tokens.
Defaults low.
These bits are used to determine the data rate of the
COM20022I 3V. The following table is for a 20 MHz
crystal: (Clock Multiplier is bypassed)
SPEED
CKP3 CKP2 CKP1 DIVISOR
0
0
0
8
2.5Mbs
0
1
0
16
1.25Mbs
1
0
0
32
625Kbs
1
1
0
64
312.5Kbs
0
0
1
128
156.25Kbs
Note: The lowest data rate achievable by the COM20022I
3V is 156.25Kbs. Defaults to 000 or 2.5Mbs. For
Clock Multiplier output clock speed greater than 20
MHz, CKP3, CKP2 and CKP1 must all be zero.
This bit, when set, will divide the arbitration clock by 2.
Memory cycle times will increase when slow arbitration is
selected.
Note: For clock multiplier output clock speeds greater
than 40 MHz, SLOWARB must be set. Defaults to
low.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Table 6.13 - Setup 2 Register
BIT
7
BIT NAME
Read Bus Timing
Select
6
5,4
Reserved
Clock Multiplier
SYMBOL
DESCRIPTION
RBUSTMG This bit is used to Disable/Enable the High Speed CPU
Read function for High Speed CPU bus support.
RBUSTMG=0: Disable (Default), RBUSTMG=1: Enable.
That is, if BUSTMG (pin 26) = 1 and RBUSTMG = 1, High
Speed CPU Read operations are enabled. It does not
influence write operation. High speed CPU Read operation
is only for non-multiplexed bus.
This bit is undefined. It must be 0.
CKUP1, 0 Higher frequency clocks are generated from the 20 MHz
crystal through the selection of these two bits as shown.
This clock multiplier is powered-down on default. After
changing the CKUP1 and CKUP0 bits, the ARCNET core
operation is stopped and the internal PLL in the clock
multiplier is awakened and it starts to generate the 40 MHz.
The lock out time of the internal PLL is 8μSec typically.
After 1 mS it is necessary to write command data '18H' to
command register for re-starting the ARCNET core
operation. EF bit must be ‘1’ if the data rate is over 5Mbps.
CAUTION: Changing the CKUP1 and CKUP0 bits must be
one time or less after releasing a hardware reset.
3
Enhanced
Functions
EF
2
No Synchronous
NOSYNC
SMSC COM20022I 3.3V Rev.C
CKUP1
CKUP0
Clock Frequency (Data Rate)
0
0
20 MHz (Up to 2.5Mbps) Default
0
1
40 MHz (Up to 5Mbps)
1
0
Reserved
1
1
80 MHz (Only 10Mbps)
Note: After changing the CKUP1 or CKUP0 bits, it is
necessary to write a command data '18H' to the
command register. Because after changing the
CKUP [1, 0] bits, the internal operation is stopped
temporarily. The writing of the command is to start
the operation.
These initializing steps are shown below.
1. Hardware reset (Power ON)
2. Change CKUP[1, 0] bit
3. Wait 1mSec (wait until stable oscillation)
4. Write command '18H' (start internal operation)
5. Start initializing routine (Execute existing software)
This bit is used to enable the new enhanced functions in the
COM20022I 3V. EF = 0: Disable (Default), EF = 1: Enable.
If EF = 0, the timing and function is the same as in the
COM20020, Revision B. See appendix “A”. EF bit must be
‘1’ if the data rate is over 5Mbps.
EF bit should be ‘1’ for new design customers.
EF bit should be ‘0’ for replacement customers.
This bit is used to enable the SYNC command during
initialization. NOSYNC= 0, Enable (Default) The line must
be idle for the RAM initialization sequence to be written.
NOSYNC= 1, Disable:) The line does not have to be idle for
the RAM initialization sequence to be written. See appendix
“A”.
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
BIT
1,0
BIT NAME
Reconfiguration
Timer 1, 0
SYMBOL
DESCRIPTION
RCNTM1,0 These bits are used to program the reconfiguration timer as
a function of maximum node count. These bits set the time
out period of the reconfiguration timer as shown below. The
time out periods shown are for 10 Mbps.
Time Out
Period
RCNTM1 RCNTM0
Max Node Count
0
0
210 mS
Up to 255 nodes
0
1
52.5 mS
Up to 64 nodes
1
0
26.25 mS
Up to 32 nodes
1
1
13.125 mS*
Up to 16 nodes
Note*: The node ID value 255 must exist in the network for
13.125 mS timeout to be valid.
Table 6.14 - Bus Control Register
BIT
7
BIT NAME
16 Bit Access
6-0
Reserved
Revision 03-08-07
SYMBOL
W16
DESCRIPTION
This bit is used to Disable/Enable the 16 bit access.
It influences only DATA register access.
W16= 0: Disable (Default); W16= 1: Enable
These bit are undefined. They must be 0.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Data Register
I/O Address 04H
Memory
Data Bus
2K x 8
INTERNAL
RAM
8
D0-D7
Address Pointer Register
I/O Address 02H
I/O Address 03H
High
Low
Memory
Address Bus
11-Bit Counter
11
Figure 6.1 - Sequential Access Operation
6.3
Internal RAM
The integration of the 2K x 8 RAM in the COM20022I 3V represents significant real estate savings. The
most obvious benefit is the 48 pin package in which the device is now placed (a direct result of the
integration of RAM). In addition, the PC board is now free of the cumbersome external RAM, external
latch, and multiplexed address/data bus and control functions which were necessary to interface to the
RAM. The integration of RAM represents significant cost savings because it isolates the system designer
from the changing costs of external RAM and it minimizes reliability problems, assembly time and costs,
and layout complexity.
6.3.1
Sequential Access Memory
The internal RAM is accessed via a pointer-based scheme. Rather than interfering with system memory,
the internal RAM is indirectly accessed through the Address High and Low Pointer Registers. The data is
channeled to and from the microcontroller via the 8-bit data register. For example: a packet in the internal
RAM buffer is read by the microcontroller by writing the corresponding address into the Address Pointer
High and Low Registers (offsets 02H and 03H). Note that the High Register should be written first,
followed by the Low Register, because writing to the Low Register loads the address. At this point the
device accesses that location and places the corresponding data into the data register. The
microcontroller then reads the data register (offset 04H) to obtain the data at the specified location. If the
Auto Increment bit is set to logic "1", the device will automatically increment the address and place the
SMSC COM20022I 3.3V Rev.C
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
next byte of data into the data register, again to be read by the microcontroller. This process is continued
until the entire packet is read out of RAM. Refer to Figure 6.1Error! Reference source not found. for an
illustration of the Sequential Access operation. When switching between reads and writes, the pointer
must first be written with the starting address. At least one cycle time should separate the pointer being
loaded and the first read (see timing parameters).
6.3.2
Access Speed
The COM20022I 3V is able to accommodate very fast access cycles to its registers and buffers. Arbitration
to the buffer does not slow down the cycle because the pointer based access method allows data to be
prefetched from memory and stored in a temporary register. Likewise, data to be written is stored in the
temporary register and then written to memory.
For systems which do not require quick access time, the arbitration clock may be slowed down by setting
bit 0 of the Setup1 Register equal to logic "1". Since the Slow Arbitration feature divides the input clock by
two, the duty cycle of the input clock may be relaxed.
6.3.3
Software Interface
The microcontroller interfaces to the COM20022I 3V via software by accessing the various registers.
These actions are described in the Internal Registers section. The software flow for accessing the data
buffer is based on the Sequential Access scheme. The basic sequence is as follows:
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
Disable Interrupts
Write to Pointer Register High (specifying Auto-Increment mode)
Write to Pointer Register Low (this loads the address)
Enable Interrupts
Read or Write the Data Register (repeat as many times as necessary to empty or fill the buffer)
The pointer may now be read to determine how many transfers were completed.
The software flow for controlling the Configuration, Node ID, Tentative ID, and Next ID registers is
generally limited to the initialization sequence and the maintenance of the network map.
Additionally, it is necessary to understand the details of how the other Internal Registers are used in the
transmit and receive sequences and to know how the internal RAM buffer is properly set up. The
sequence of events that tie these actions together is discussed as follows.
6.3.4
Selecting RAM Page Size
During normal operation, the 2K x 8 of RAM is divided into four pages of 512 bytes each. The page to be
used is specified in the "Enable Transmit (Receive) from (to) Page fnn" command, where "nn" specifies
page 0, 1, 2, or 3. This allows the user to have constant control over the allocation of RAM.
When the Offset bit "f" (bit 5 of the "Enable Transmit (Receive) from (to) Page fnn" command word) is set
to logic "1", an offset of 256 bytes is added to the page specified. For example: to transmit from the second
half of page 0, the command "Enable Transmit from Page fnn" (fnn=100 in this case) is issued by writing
0010 0011 to the Command Register. This allows a finer resolution of the buffer pages without affecting
software compatibility. This scheme is useful for applications which frequently use packet sizes of 256
bytes or less, especially for microcontroller systems with limited memory capacity. The remaining portions
of the buffer pages which are not allocated for current transmit or receive packets may be used as
temporary storage for previous network data, packets to be sent later, or as extra memory for the system,
which may be indirectly accessed.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
If the device is configured to handle both long and short packets (see "Define Configuration" command),
then receive pages should always be 512 bytes long because the user never knows what the length of the
receive packet will be. In this case, the transmit pages may be made 256 bytes long, leaving at least 512
bytes free at any given time. Even if the Command Chaining operation is being used,512 bytes is still
guaranteed to be free because Command Chaining only requires two pages for transmit and two for
receive (in this case, two 256 byte pages for transmit and two 512 byte pages for receive, leaving 512
bytes free). Please note that it is the responsibility of software to reserve 512 bytes for each receive page if
the device is configured to handle long packets. The COM20022I 3V does not check page boundaries
during reception. If the device is configured to handle only short packets, then both transmit and receive
pages may be allocated as 256 bytes long, freeing at least 1KByte at any given time.
Even if the Command Chaining operation is being used, 1KByte is still guaranteed to be free because
Command Chaining only requires two pages for transmit and two for receive (in this case, a total of four
256 byte pages, leaving 1K free).
The general rule which may be applied to determine where in RAM a page begins is as follows:
Address = (nn x 512) + (f x 256).
SMSC COM20022I 3.3V Rev.C
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Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
ADDRESS
0
SHORT PACKET
FORMAT
LONG PACKET
FORMAT
SID
ADDRESS
0
1
DID
1
2
COUNT = 256-N
2
0
3
COUNT = 512-N
NOT USED
COUNT
DATA BYTE 1
SID
DID
NOT USED
DATA BYTE 2
COUNT
DATA BYTE 1
DATA BYTE 2
DATA BYTE N-1
255
DATA BYTE N
DATA BYTE N-1
NOT USED
511
511
DATA BYTE N
N = DATA PACKET LENGTH
SID = SOURCE ID
DID = DESTINATION ID
(DID = 0 FOR BROADCASTS)
Figure 6.2 - RAM Buffer Packet Configuration
6.3.5
Transmit Sequence
During a transmit sequence, the microcontroller selects a 256 or 512 byte segment of the RAM buffer and
writes into it. The appropriate buffer size is specified in the "Define Configuration" command. When long
packets are enabled, the COM20022I 3V interprets the packet as either a long or short packet, depending
on whether the buffer address 2 contains a zero or non-zero value. The format of the buffer is shown in
Figure 5.3. Address 0 contains the Source Identifier (SID); Address 1 contains the Destination Identifier
(DID); Address 2 (COUNT) contains, for short packets, the value 256-N, where N represents the number
of information bytes in the message, or for long packets, the value 0, indicating that it is indeed a long
packet. In the latter case, Address 3 (COUNT) would contain the value 512-N, where N represents the
number of information bytes in the message. The SID in Address 0 is used by the receiving node to reply
to the transmitting node. The COM20022I 3V puts the local ID in this location, therefore it is not necessary
to write into this location. Please note that a short packet may contain between 1 and 253 data bytes,
while a long packet may contain between 257 and 508 data bytes. A minimum value of 257 exists on a
long packet so that the COUNT is expressible in eight bits. This leaves three exception packet lengths
which do not fit into either a short or long packet; packet lengths of 254, 255, or 256 bytes. If packets of
these lengths must be sent, the user must add dummy bytes to the packet in order to make the packet fit
into a long packet.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Once the packet is written into the buffer, the microcontroller awaits a logic "1" on the TA bit, indicating that
a previous transmit command has concluded and another may be issued. Each time the message is
loaded and a transmit command issued, it will take a variable amount of time before the message is
transmitted, depending on the traffic on the network and the location of the token at the time the transmit
command was issued. The conclusion of the Transmit Command will generate an interrupt if the Interrupt
Mask allows it. If the device is configured for the Command Chaining operation, please see the Command
Chaining section for further detail on the transmit sequence. Once the TA bit becomes a logic "1", the
microcontroller may issue the "Enable Transmit from Page fnn" command, which resets the TA and TMA
bits to logic "0". If the message is not a BROADCAST, the COM20022I 3V automatically sends a FREE
BUFFER ENQUIRY to the destination node in order to send the message. At this point, one of four
possibilities may occur.
The first possibility is if a free buffer is available at the destination node, in which case it responds with an
ACKnowledgement. At this point, the COM20022I 3V fetches the data from the Transmit Buffer and
performs the transmit sequence. If a successful transmit sequence is completed, the TMA bit and the TA
bit are set to logic "1". If the packet was not transmitted successfully, TMA will not be set. A successful
transmission occurs when the receiving node responds to the packet with an ACK. An unsuccessful
transmission occurs when the receiving node does not respond to the packet.
The second possibility is if the destination node responds to the Free Buffer Enquiry with a Negative
AcKnowledgement. A NAK occurs when the RI bit of the destination node is a logic "1". In this case, the
token is passed on from the transmitting node to the next node. The next time the transmitter receives the
token, it will again transmit a FREE BUFFER ENQUIRY. If a NAK is again received, the token is again
passed onto the next node. The Excessive NAK bit of the Diagnostic Status Register is used to prevent an
endless sending of FBE's and NAK's. If no limit of FBE-NAK sequences existed, the transmitting node
would continue issuing a Free Buffer Enquiry, even though it would continuously receive a NAK as a
response. The EXCNAK bit generates an interrupt (if enabled) in order to tell the microcontroller to disable
the transmitter via the "Disable Transmitter" command. This causes the transmission to be abandoned
and the TA bit to be set to a logic "1" when the node next receives the token, while the TMA bit remains at
a logic "0". Please refer to the Improved Diagnostics section for further detail on the EXCNAK bit.
The third possibility which may occur after a FREE BUFFER ENQUIRY is issued is if the destination node
does not respond at all. In this case, the TA bit is set to a logic "1", while the TMA bit remains at a logic
"0". The user should determine whether the node should try to reissue the transmit command.
The fourth possibility is if a non-traditional response is received (some pattern other than ACK or NAK,
such as noise). In this case, the token is not passed onto the next node, which causes the Lost Token
Timer of the next node to time out, thus generating a network reconfiguration.
The "Disable Transmitter" command may be used to cancel any pending transmit command when the
COM20022I 3V next receives the token. Normally, in an active network, this command will set the TA
status bit to a logic "1" when the token is received. If the "Disable Transmitter" command does not cause
the TA bit to be set in the time it takes the token to make a round trip through the network, one of three
situations exists. Either the node is disconnected from the network, or there are no other nodes on the
network, or the external receive circuitry has failed. These situations can be determined by either using
the improved diagnostic features of the COM20022I 3V or using another software timeout which is greater
than the worst case time for a round trip token pass, which occurs when all nodes transmit a maximum
length message.
6.3.6
Receive Sequence
A receive sequence begins with the RI status bit becoming a logic "1", which indicates that a previous
reception has concluded. The microcontroller will be interrupted if the corresponding bit in the Interrupt
Mask Register is set to logic "1". Otherwise, the microcontroller must periodically check the Status
Register. Once the microcontroller is alerted to the fact that the previous reception has concluded, it may
issue the "Enable Receive to Page fnn" command, which resets the RI bit to logic "0" and selects a new
page in the RAM buffer. Again, the appropriate buffer size is specified in the "Define Configuration"
command. Typically, the page which just received the data packet will be read by the microcontroller at
SMSC COM20022I 3.3V Rev.C
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
this point. Once the "Enable Receive to Page fnn" command is issued, the microcontroller attends to other
duties.
There is no way of knowing how long the new reception will take, since another node may transmit a
packet at any time. When another node does transmit a packet to this node, and if the "Define
Configuration" command has enabled the reception of long packets, the COM20022I 3V interprets the
packet as either a long or short packet, depending on whether the content of the buffer location 2 is zero or
non-zero. The format of the buffer is shown in Figure 5.3. Address 0 contains the Source Identifier (SID),
Address 1 contains the Destination Identifier (DID), and Address 2 contains, for short packets, the value
256-N, where N represents the message length, or for long packets, the value 0, indicating that it is indeed
a long packet. In the latter case, Address 3 contains the value 512-N, where N represents the message
length. Note that on reception, the COM20022I 3V deposits packets into the RAM buffer in the same
format that the transmitting node arranges them, which allows for a message to be received and then
retransmitted without rearranging any bytes in the RAM buffer other than the SID and DID. Once the
packet is received and stored correctly in the selected buffer, the COM20022I 3V sets the RI bit to logic "1"
to signal the microcontroller that the reception is complete.
MSB
TRI
LSB
RI
TA
POR
TEST
RECON
TRI
TMA
TTA
TMA
TTA
Figure 6.3 - Command Chaining Status Register Queue
6.4
Command Chaining
The Command Chaining operation allows consecutive transmissions and receptions to occur without host
microcontroller intervention.
Through the use of a dual two-level FIFO, commands to be transmitted and received, as well as the status
bits, are pipelined.
In order for the COM20022I 3V to be compatible with previous SMSC ARCNET device drivers, the device
defaults to the non-chaining mode. In order to take advantage of the Command Chaining operation, the
Command Chaining Mode must be enabled via a logic "1" on bit 6 of the Configuration Register.
In Command Chaining, the Status Register appears as in Figure 6.3.
The following is a list of Command Chaining guidelines for the software programmer. Further detail can be
found in the Transmit Command Chaining and Receive Command Chaining sections.
ƒ
ƒ
ƒ
ƒ
Revision 03-08-07
The device is designed such that the interrupt service routine latency does not affect performance.
Up to two outstanding transmissions and two outstanding receptions can be pending at any given
time. The commands may be given in any order.
Up to two outstanding transmit interrupts and two outstanding receive interrupts are stored by the
device, along with their respective status bits.
The Interrupt Mask bits act on TTA (Rising Transition on Transmitter Available) for transmit operations
and TRI (Rising Transition of Receiver Inhibited) for receive operations. TTA is set upon completion
of a packet transmission only. TRI is set upon completion of a packet reception only. Typically there is
no need to mask the TTA and TRI bits after clearing the interrupt.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
ƒ
6.4.1
The traditional TA and RI bits are still available to reflect the present status of the device.
Transmit Command Chaining
When the processor issues the first "Enable Transmit to Page fnn" command, the COM20022I 3V
responds in the usual manner by resetting the TA and TMA bits to prepare for the transmission from the
specified page. The TA bit can be used to see if there is currently a transmission pending, but the TA bit is
really meant to be used in the non-chaining mode only. The TTA bits provide the relevant information for
the device in the Command Chaining mode.
In the Command Chaining Mode, at any time after the first command is issued, the processor can issue a
second "Enable Transmit from Page fnn" command. The COM20022I 3V stores the fact that the second
transmit command was issued, along with the page number.
After the first transmission is completed, the COM20022I 3V updates the Status Register by setting the
TTA bit, which generates an interrupt. The interrupt service routine should read the Status Register. At
this point, the TTA bit will be found to be a logic "1" and the TMA (Transmit Message Acknowledge) bit will
tell the processor whether the transmission was successful. After reading the Status Register, the "Clear
Transmit Interrupt" command is issued, thus resetting the TTA bit and clearing the interrupt. Note that
only the "Clear Transmit Interrupt" command will clear the TTA bit and the interrupt. It is not necessary,
however, to clear the bit or the interrupt right away because the status of the transmit operation is double
buffered in order to retain the results of the first transmission for analysis by the processor. This
information will remain in the Status Register until the "Clear Transmit Interrupt" command is issued. Note
that the interrupt will remain active until the command is issued, and the second interrupt will not occur
until the first interrupt is acknowledged. The COM20022I 3V guarantees a minimum of 200nS (at EF=1)
interrupt inactive time interval between interrupts. The TMA bit is also double buffered to reflect whether
the appropriate transmission was a success. The TMA bit should only be considered valid after the
corresponding TTA bit has been set to a logic "1". The TMA bit never causes an interrupt.
When the token is received again, the second transmission will be automatically initiated after the first is
completed by using the stored "Enable Transmit from Page fnn" command. The operation is as if a new
"Enable Transmit from Page fnn" command has just been issued. After the first Transmit status bits are
cleared, the Status Register will again be updated with the results of the second transmission and a
second interrupt resulting from the second transmission will occur. The COM20022I 3V guarantees a
minimum of 200ns (at EF=1) interrupt inactive time interval before the following edge.
The Transmitter Available (TA) bit of the Interrupt Mask Register now masks only the TTA bit of the Status
Register, not the TA bit as in the non-chaining mode. Since the TTA bit is only set upon transmission of a
packet (not by RESET), and since the TTA bit may easily be reset by issuing a "Clear Transmit Interrupt"
command, there is no need to use the TA bit of the Interrupt Mask Register to mask interrupts generated
by the TTA bit of the Status Register.
In Command Chaining mode, the "Disable Transmitter" command will cancel the oldest transmission. This
permits canceling a packet destined for a node not ready to receive. If both packets should be canceled,
two "Disable Transmitter" commands should be issued.
6.4.2
Receive Command Chaining
Like the Transmit Command Chaining operation, the processor can issue two consecutive "Enable
Receive from Page fnn" commands.
After the first packet is received into the first specified page, the TRI bit of the Status Register will be set to
logic "1", causing an interrupt. Again, the interrupt need not be serviced immediately. Typically, the
interrupt service routine will read the Status Register. At this point, the RI bit will be found to be a logic "1".
After reading the Status Register, the "Clear Receive Interrupt" command should be issued, thus resetting
the TRI bit and clearing the interrupt. Note that only the "Clear Receive Interrupt" command will clear the
SMSC COM20022I 3.3V Rev.C
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Datasheet
TRI bit and the interrupt. It is not necessary, however, to clear the bit or the interrupt right away because
the status of the receive operation is double buffered in order to retain the results of the first reception for
analysis by the processor, therefore the information will remain in the Status Register until the "Clear
Receive Interrupt" command is issued. Note that the interrupt will remain active until the "Clear Receive
Interrupt" command is issued, and the second interrupt will be stored until the first interrupt is
acknowledged. A minimum of 200nS (at EF=1) interrupt inactive time interval between interrupts is
guaranteed.
The second reception will occur as soon as a second packet is sent to the node, as long as the second
"Enable Receive to Page fnn" command was issued. The operation is as if a new "Enable Receive to
Page fnn" command has just been issued. After the first Receive status bits are cleared, the Status
Register will again be updated with the results of the second reception and a second interrupt resulting
from the second reception will occur.
In the COM20022I 3V, the Receive Inhibit (RI) bit of the Interrupt Mask Register now masks only the TRI
bit of the Status Register, not the RI bit as in the non-chaining mode. Since the TRI bit is only set upon
reception of a packet (not by RESET), and since the TRI bit may easily be reset by issuing a "Clear
Receive Interrupt" command, there is no need to use the RI bit of the Interrupt Mask Register to mask
interrupts generated by the TRI bit of the Status Register. In Command Chaining mode, the "Disable
Receiver" command will cancel the oldest reception, unless the reception has already begun. If both
receptions should be canceled, two "Disable Receiver" commands should be issued.
6.4.3
Reset Details
6.4.3.1
Internal Reset Logic
The COM20022I 3V includes special reset circuitry to guarantee smooth operation during reset. Special
care is taken to assure proper operation in a variety of systems and modes of operation. The COM20022I
3V contains digital filter circuitry and a Schmitt Trigger on the nRESET signal to reject glitches in order to
ensure fault-free operation.
The COM20022I 3V supports two reset options; software and hardware reset. A software reset is
generated when a logic "1" is written to bit 7 of the Configuration Register. The device remains in reset as
long as this bit is set. The software reset does not affect the microcontroller
interface
modes
determined after hardware reset, nor does it affect the contents of the Address Pointer Registers, the
Configuration Register, or the Setup1 Register. A hardware reset occurs when a low signal is asserted on
the nRESET input. The minimum reset pulse width is 5TXTL. This pulse width is used by the internal digital
filter, which filters short glitches to allow only valid resets to occur
Upon reset, the transmitter portion of the device is disabled and the internal registers assume those states
outlined in the Internal Registers section. After the nRESET signal is removed the user may write to the
internal registers. Since writing a non-zero value to the Node ID Register wakes up the COM20022I 3V
core, the Setup1 Register should be written before the Node ID Register. Once the Node ID Register is
written to, the COM20022I 3V reads the value and executes two write cycles to the RAM buffer. Address 0
is written with the data D1H and address 1 is written with the Node ID. The data pattern D1H was chosen
arbitrarily, and is meant to provide assurance of proper microsequencer operation.
6.5
Initialization Sequence
6.5.1
Bus Determination
Writing to and reading from an odd address location from the COM20022I 3V's address space causes the
COM20022I 3V to determine the appropriate bus interface. When the COM20022I 3V is powered on the
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
internal registers may be written to. Since writing a non-zero value to the Node ID Register wakes up the
core, the Setup1 Register should be written to before the Node ID Register. Until a non-zero value is
placed into the NID Register, no microcode is executed, no tokens are passed by this node, and no
reconfigurations are generated by this node. Once a non-zero value is placed in the register, the core
wakes up, but the node will not attempt to join the network until the TX Enable bit of the Configuration
Register is set.
Before setting the TX Enable bit, the software may make some determinations. The software may first
observe the Receive Activity and the Token Seen bits of the Diagnostic Status Register to verify the health
of the receiver and the network.
Next, the uniqueness of the Node ID value placed in the Node ID Register is determined. The TX Enable
bit should still be a logic "0" until it is ensured that the Node ID is unique. If this node ID already exists, the
Duplicate ID bit of the Diagnostic Status Register is set after a maximum of 210mS (or 420mS if the ET1
and ET2 bits are other than 1,1). To determine if another node on the network already has this ID, the
COM20022I 3V compares the value in the Node ID Register with the DID's of the token, and determines
whether there is a response to it. Once the Diagnostic Status Register is read, the DUPID bit is cleared.
The user may then attempt a new ID value, wait 210mS before checking the Duplicate ID bit, and repeat
the process until a unique Node ID is found. At this point, the TX Enable bit may be set to allow the node
to join the network. Once the node joins the network, a reconfiguration occurs, as usual, thus setting the
MYRECON bit of the Diagnostic Status Register.
The Tentative ID Register may be used to build a network map of all the nodes on the network, even once
the COM20022I 3V has joined the network. Once a value is placed in the Tentative ID Register, the
COM20022I 3V looks for a response to a token whose DID matches the Tentative ID Register. The
software can record this information and continue placing Tentative ID values into the register to continue
building the network map. A complete network map is only valid until nodes are added to or deleted from
the network. Note that a node cannot detect the existence of the next logical node on the network when
using the Tentative ID. To determine the next logical node, the software should read the Next ID Register.
6.6
Improved Diagnostics
The COM20022I 3V allows the user to better manage the operation of the network through the use of the
internal Diagnostic Status Register.
A high level on the My Reconfiguration (MYRECON) bit indicates that the Token Reception Timer of this
node expired, causing a reconfiguration by this node. After the Reconfiguration (RECON) bit of the Status
Register interrupts the microcontroller, the interrupt service routine will typically read the MYRECON bit of
the Diagnostic Status Register. Reading the Diagnostic Status Register resets the MYRECON bit.
Successive occurrences of a logic "1" on the MYRECON bit indicates that a problem exists with this node.
At that point, the transmitter should be disabled so that the entire network is not held down while the node
is being evaluated.
The Duplicate ID (DUPID) bit is used before the node joins the network to ensure that another node with
the same ID does not exist on the network. Once it is determined that the ID in the Node ID Register is
unique, the software should write a logic "1" to bit 5 of the Configuration Register to enable the basic
transmit function. This allows the node to join the network.
The Receive Activity (RCVACT) bit of the Diagnostic Status Register will be set to a logic "1" whenever
activity (logic "1") is detected on the RXIN pin.
The Token Seen (TOKEN) bit is set to a logic "1" whenever any token has been seen on the network
(except those tokens transmitted by this node).
The RCVACT and TOKEN bits may help the user to troubleshoot the network or the node. If unusual
events are occurring on the network, the user may find it valuable to use the TXEN bit of the Configuration
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Datasheet
Register to qualify events. Different combinations of the RCVACT, TOKEN, and TXEN bits, as shown
indicate different situations:
6.6.1
Normal Results:
RCVACT=1, TOKEN=1, TXEN=0: The node is not part of the network. The network is operating properly
without this node.
RCVACT=1, TOKEN=1, TXEN=1: The node sees receive activity and sees the token. The basic transmit
function is enabled. Network and node are operating properly.
MYRECON=0, DUPID=0, RCVACT=1, TXEN=0, TOKEN=1: Single node network.
6.6.2
Abnormal Results:
RCVACT=1, TOKEN=0, TXEN=X: The node sees receive activity, but does not see the token. Either no
other nodes exist on the network, some type of data corruption exists, the media driver is malfunctioning,
the topology is set up incorrectly, there is noise on the network, or a reconfiguration is occurring.
RCVACT=0, TOKEN=0, TXEN=1: No receive activity is seen and the basic transmit function is enabled.
The transmitter and/or receiver are not functioning properly.
RCVACT=0, TOKEN=0, TXEN=0: No receive activity and basic transmit function disabled. This node is
not connected to the network.
The Excessive NAK (EXCNAK) bit is used to replace a timeout function traditionally implemented in
software. This function is necessary to limit the number of times a sender issues a FBE to a node with no
available buffer. When the destination node replies to 128 FBEs with 128 NAKs or 4 FBEs with 4 NAKs,
the EXCNAK bit of the sender is set, generating an interrupt. At this point the software may abandon the
transmission via the "Disable Transmitter" command. This sets the TA bit to logic "1" when the node next
receives the token, to allow a different transmission to occur. The timeout value for the EXNACK bit (128
or 4) is determined by the FOUR-NAKS bit on the Setup1 Register.
The user may choose to wait for more NAK's before disabling the transmitter by taking advantage of the
wraparound counter of the EXCNAK bit. When the EXCNAK bit goes high, indicating 128 or 4 NAKs, the
"POR Clear Flags" command maybe issued to reset the bit so that it will go high again after another
count of 128 or 4. The software may count the number of times the EXCNAK bit goes high, and once the
final count is reached, the "Disable Transmitter" command may be issued.
The New Next ID bit permits the software to detect the withdrawal or addition of nodes to the network.
The Tentative ID bit allows the user to build a network map of those nodes existing on the network. This
feature is useful because it minimizes the need for human intervention. When a value placed in the
Tentative ID Register matches the Node ID of another node on the network, the TENTID bit is set, telling
the software that this NODE ID already exists on the network. The software should periodically place
values in the Tentative ID Register and monitor the New Next ID bit to maintain an updated network map.
6.6.3
Oscillator
The COM20022I 3V contains circuitry which, in conjunction with an external parallel resonant crystal or
TTL clock, forms an oscillator.
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
If an external crystal is used, two capacitors are needed (one from each leg of the crystal to ground). No
external resistor is required, since the COM20022I 3V contains an internal resistor. The crystal must have
an accuracy of 0.020% or better. The oscillation frequency range is from 10 MHz to 20 MHz.
The crystal must have an accuracy of 0.010% or better when the internal clock multiplier is turned on. The
oscillation frequency must be 20MHz when the internal clock multiplier is turned on.
The XTAL2 side of the crystal may be loaded with a single 74HC-type buffer in order to generate a clock
for other devices.
The user may attach an external TTL clock, rather than a crystal, to the XTAL1 signal. In this case, a
390Ω pull-up resistor is required on XTAL1, while XTAL2 should be left unconnected.
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Chapter 7
7.1
Operational Description
Maximum Guaranteed Ratings*
Operating Temperature Range ...............................................................................................-40oC to +85oC
Storage Temperature Range ................................................................................................-55oC to +150oC
o
Lead Temperature (soldering, 10 seconds) ....................................................................................... +325 C
Positive Voltage on any pin expect XTAL1 and XTAL2, with respect to ground .................................. +5.5V
Positive Voltage on XTAL1 and XTAL2 pin, with respect to ground ................................................VDD+0.3V
Negative Voltage on any pin, with respect to ground ............................................................................. -0.3V
Maximum VDD .......................................................................................................................................... +5V
* Stresses above those listed may cause permanent damage to the device. This is a stress rating only and
functional operation of the device at these or any other condition above those indicated in the operational
sections of this specification is not implied.
Note:
When powering this device from laboratory or system power supplies, it is important that the Absolute
Maximum Ratings not be exceeded or device failure can result. Some power supplies exhibit voltage
spikes or "glitches" on their outputs when the AC power is switched on or off. In addition, voltage
transients on the AC power line may appear on the DC output. If this possibility exists it is suggested that
a clamp circuit be used.
7.2
DC Electrical Characteristics
VDD= 3.3v±5%
TA=-40oC to +85oC
PARAMETER
SYMBOL
VIL1
Low Input Voltage 1
(All inputs except XTAL1)
MIN
-0.3
TYP
MAX
0.8
UNIT
V
COMMENT
TTL Level
High Input Voltage 1
(All inputs except XTAL1)
Low Input Voltage 2
(XTAL1)
VIH1
2.0
5.5
V
VIL2
-0.3
0.2xVDD
V
High Input Voltage 2
(XTAL1)
Low Output Voltage 1
(nTXEN)
VIH2
0.8xVDD
VDD+0.3
V
0.4
V
ISINK=4mA
V
ISOURCE=-2mA
High Output Voltage 1
(nTXEN)
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VOL1
VOH1
2.4
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DATASHEET
External Clock Input
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
PARAMETER
Low Output Voltage 2
(AD0-AD2, D3-D15,
nINTR, nPULSE1 in
Push/Pull Mode,
nPULSE2, nIOCS16)
High Output Voltage 2
(AD0-AD2, D3-D15,
nINTR, nPULSE1 in
Push/Pull Mode, PULSE2,
nIOCS16)
Low Output Voltage 3
(nPULSE1 in Open-Drain
Mode)
Dynamic VDD Supply
Current
SYMBOL
VOL2
MIN
VOH2
2.4
TYP
VOL3
0.4
IDD1
IDD2
40
60
Input Pull-up Current
(nPULSE1 in Open-Drain
Mode, A1, AD0-AD2,
D3-D15, BUSTMG)
IP
80
Input Leakage Current
(All inputs except A1,
AD0-AD2, D3-D15,
XTAL1, BUSTMG)
IL
SMSC COM20022I 3.3V Rev.C
MAX
0.4
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DATASHEET
UNIT
V
COMMENT
ISINK=8mA
V
ISOURCE=-4mA
V
ISINK=8mA
Open Drain Driver
mA
mA
200
μA
5 Mbps
10 Mbps
All Outputs Open
VIN=0.0V
±10
μA
VSS < VIN < VDD
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
CAPACITANCE (TA = 25°C; fC = 1MHz; VDD = 0V)
Output and I/O pins capacitive load specified as follows:
PARAMETER
Input Capacitance
Output Capacitance 1
(All outputs except XTAL2)
SYMBOL
CIN
COUT1
MIN
TYP
MAX
5.0
45
UNIT
pF
pF
COMMENT
Maximum Capacitive
Load which can be
supported by each
output.
AC Measurements are taken at the following points:
Inputs:
Outputs:
t
t
2.0V
2.4V
1.4V
50%
0.8V
0.4V
t
2.4V
2.0V
1.4V
0.4V
50%
0.8V
t
Inputs are driven at 2.4V for logic "1" and 0.4 V for logic "0" except XTAL1 pin.
Outputs are measured at 2.0V min. for logic "1" and 0.8V max. for logic "0".
Figure 7.1 - AC Measurements
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Chapter 8
Timing Diagrams
AD0-AD2,
D3-D15
VALID DATA
VALID
t1
t2,
t4
nCS
t3
t12
t11
ALE
t6
t5
nDS
t7
t13
t14
Note 2
t8
DIR
t15
nIOCS16
Previous Value
t9
t16
Invalid
t10
Valid Value
MUST BE: BUSTMG pin = HIGH and RBUSTMG bit = 0
Parameter
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
t13
t14
t15
t16
Address Setup to ALE Low
Address Hold from ALE Low
nCS Setup to ALE Low
nCS Hold from ALE Low
ALE Low to nDS Low
nDS Low to Valid Data
nDS High to Data High Impedance
Cycle Time (nDS Low to Next Time Low)
DIR Setup to nDS Active
DIR Hold from nDS Inactive
ALE High Width
ALE Low Width
nDS Low Width
nDS High Width
nIOCS16 Hold Delay from ALE Low
nIOCS16 Output Delay from ALE Low
min
max
20
10
10
10
15
0
40
20
4TARB*
10
10
20
20
60
20
0
40
units
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
Note 1: The Microcontroller typically accesses the COM20022 on every other cycle.
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
Note 2: Read cycle for Address Pointer Low/High Registers occurring after an access
to Data Register requires a minimum of 5TARB from the trailing edge of nDS to
the leading edge of the next nDS.
Note 2 is applied to an access to Data Register by DMA transfer.
Figure 8.1 - Multiplexed Bus, 68XX-Like Control Signals; Read Cycle
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Datasheet
AD0-AD2,
D3-D15
VALID DATA
VALID
t1
t2,
t4
nCS
t3
ALE
t10
t9
t6
nRD
t7
t5
nWR
t11
t13 Note 3
t14
nIOCS16
Previous Value
t8
t12
t15
Invalid
Note 2
Valid Value
MUST BE: BUSTMG pin = HIGH and RBUSTMG bit = 0
Parameter
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
t13
t14
t15
Address Setup to ALE Low
Address Hold from ALE Low
nCS Setup to ALE Low
nCS Hold from ALE Low
ALE Low to nRD Low
nRD Low to Valid Data
nRD High to Data High Impedance
Cycle Time (nRD Low to Next Time Low)
ALE High Width
ALE Low Width
nRD Low Width
nRD High Width
nWR
to nRD Low
nIOCS16 Hold Delay from ALE Low
nIOCS16 Output Delay from ALE Low
min
max
20
10
10
10
15
0
40
20
4TARB*
20
20
60
20
20
0
40
units
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
Note 1: The Microcontroller typically accesses the COM20022 on every other cycle.
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
Note 2: Read cycle for Address Pointer Low/High Registers occurring after a read from
Data Register requires a minimum of 5TARB from the trailing edge of nRD to the
leading edge of the next nRD.
Note 3: Read cycle for Address Pointer Low/High Registers occurring after a write to
Data Register requires a minimum of 5TARB from the trailing edge of nWR to the
leading edge of nRD.
Notes 2 and 3 are applied to an access to Data Register by DMA transfer.
Figure 8.2 - Multiplexed Bus, 80XX-Like Control Signals; Read Cycle
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
AD0-AD2,
D3-D15
VALID DATA
VALID
t1
t2,
t4
nCS
t3
t12
t11
ALE
t7
t5
t6
nDS
Note 2
t8**
t13
DIR
t14
t8
t16
t10
t9
t15
nIOCS16
Previous Value
Invalid
Valid Value
MUST BE: BUSTMG pin = HIGH
min
Parameter
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
t13
t14
t15
t16
Address Setup to ALE Low
Address Hold from ALE Low
nCS Setup to ALE Low
nCS Hold from ALE Low
ALE Low to nDS Low
Valid Data Setup to nDS High
Data Hold from nDS High
Cycle Time (nDS
to Next
)**
DIR Setup to nDS Active
DIR Hold from nDS Inactive
ALE High Width
ALE Low Width
nDS Low Width
nDS High Width
nIOCS16 Hold Delay from ALE Low
nIOCS16 Output Delay from ALE Low
20
10
10
10
15
30
10
4TARB*
10
10
20
20
20
20
0
max
units
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
40
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
The Microcontroller typically accesses the COM20022 on every other cycle.
Note 1:
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
** Note 2:
Any cycle occurring after a write to Address Pointer Low Register requires a
minimum of 4TARB from the trailing edge of nDS to the leading edge of the
next nDS.
Write cycle for Address Pointer Low Register occurring after an access to
Data Register requires a minimum of 5TARB from the trailing edge of nDS to
the leading edge of the next nDS.
Note 2 is applied to an access to Data Register by DMA transfer.
Figure 8.3 - Multiplexed Bus, 68XX-Like Control Signals; Write Cycle
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
AD0-AD2,
D3-D15
VALID
t1
VALID DATA
t2,
t4
nCS
t3
t10
t9
ALE
t7
t5
nWR
t6
Note 2
t8**
t15
t12
t11
t13 Note 3
nRD
t8
t14
nIOCS16
Previous Value
Invalid
Valid Value
MUST BE: BUSTMG pin = HIGH
min
Parameter
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
t13
t14
t15
Address Setup to ALE Low
Address Hold from ALE Low
nCS Setup to ALE Low
nCS Hold from ALE Low
ALE Low to nDS Low
Valid Data Setup to nDS High
Data Hold from nDS High
Cycle Time (nWR
to Next
)**
ALE High Width
ALE Low Width
nWR Low Width
nWR High Width
nRD
to nWR Low
nIOCS16 Hold Delay from ALE Low
nIOCS16 Output Delay from ALE Low
max
units
40
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
20
10
10
10
15
30
10
4TARB*
20
20
20
20
20
0
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
The Microcontroller typically accesses the COM20022 on every other cycle.
Note 1:
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
** Note 2:
Any cycle occurring after a write to Address Pointer Low Register requires a
minimum of 4TARB from the trailing edge of nWR to the leading edge of the
next nWR.
Write cycle for Address Pointer Low Register occurring after a write to Data
Register requires a minimum of 5TARB from the trailing edge of nWR to the
leading edge of the next nWR.
Note 3: Write cycle for Address Pointer Low Register occurring after a read from Data
Register requires a minimum of 5TARB from the trailing edge of nRD to the
leading edge of nWR.
Notes 2 and 3 are applied to an access to Data Register by DMA transfer.
Figure 8.4 - Multiplexed Bus, 80XX-Like Control Signals; Write Cycle
Revision 03-08-07
Page 56
DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
VALID
A0-A2
t1
t2
nCS
t4
t3
t5
Note 3
t10
nRD
t8
t7
t6
nWR
D0-D15
VALID DATA
t11
nIOCS16
t9
Note 2
t12
VALID VALUE
CASE 1: BUSTMG pin = HIGH and RBUSTMG bit = 0
Parameter
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
Address Setup to nRD Active
Address Hold from nRD Inactive
nCS Setup to nRD Active
nCS Hold from nRD Inactive
Cycle Time (nRD Low to Next Time Low)
nRD Low to Valid Data
nRD High to Data High Impedance
nRD Low Width
nRD High Width
nWR
to nRD Low
nIOCS16 Output Delay from nCS Low
nIOCS16 Hold Delay from nCS High
min
max
units
40**
20
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
15
10
5**
0
4TARB*
0
60
20
20
40***
0****
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
** nCS may become active after control becomes active, but the access time (t6)
will now be 45nS measured from the leading edge of nCS.
*** t11 is measured from the latest active (valid) timing among nCS, A0-A2.
**** t12 is measured from the earliest inactive (invalid) timing among nCS, A0-A2.
Note 1: The Microcontroller typically accesses the COM20022 on every other cycle.
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
Note 2: Read cycle for Address Pointer Low/High Registers occurring after a read from
Data Register requires a minimum of 5TARB from the trailing edge of nRD to the
leading edge of the next nRD.
Note 3: Read cycle for Address Pointer Low/High Registers occurring after a write to
Data Register requires a minimum of 5TARB from the trailing edge of nWR to the
leading edge of nRD.
Notes 2 and 3 are applied to an access to Data Register by DMA transfer.
Figure 8.5 - Non-Multiplexed Bus, 80XX-Like Control Signals; Read Cycle
SMSC COM20022I 3.3V Rev.C
Page 57
DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
VALID
A0-A2
t1
t2
nCS
t4
t3
t5
Note 3
t10
nRD
t8
t7
t6
nWR
D0-D15
t9
Note 2
VALID DATA
t11
nIOCS16
t12
VALID VALUE
CASE 2: BUSTMG pin = LOW or RBUSTMG bit = 1
Parameter
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
Address Setup to nRD Active
Address Hold from nRD Inactive
nCS Setup to nRD Active
nCS Hold from nRD Inactive
Cycle Time (nRD Low to Next Time Low)
nRD Low to Valid Data
nRD High to Data High Impedance
nRD Low Width
nRD High Width
nWR
to nRD Low
nIOCS16 Output Delay from nCS Low
nIOCS16 Hold Delay from nCS High
min
max
units
60**
20
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
-5
0
-5
0
4TARB*+30
0
100
30
20
40***
0****
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
** t6 is measured from the latest active (valid) timing among nCS, nRD, A0-A2.
*** t11 is measured from the latest active (valid) timing among nCS, A0-A2.
**** t12 is measured from the earliest inactive (invalid) timing among nCS, A0-A2.
Note 1: The Microcontroller typically accesses the COM20022 on every other cycle.
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
Note 2: Read cycle for Address Pointer Low/High Registers occurring after a read from
Data Register requires a minimum of 5TARB from the trailing edge of nRD to the
leading edge of the next nRD.
Note 3: Read cycle for Address Pointer Low/High Registers occurring after a write to
Data Register requires a minimum of 5TARB from the trailing edge of nWR to the
leading edge of nRD.
Notes 2 and 3 are applied to an access to Data Register by DMA transfer.
Figure 8.6 - Non-Multiplexed Bus, 80XX-Like Control Signals; Read Cycle
Revision 03-08-07
Page 58
DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
A0-A2
VALID
t1
t2
nCS
t4
t3
DIR
t7
t5
t6
t10
nDS
t9
t8
D0-D15
t11
Note 2
VALID DATA
t12
t13
nIOCS16
VALID VALUE
CASE 1: BUSTMG pin = HIGH and RBUSTMG bit = 0
Parameter
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
t13
Address Setup to nDS Active
Address Hold from nDS Inactive
nCS Setup to nDS Active
nCS Hold from nDS Inactive
DIR Setup to nDS Active
Cycle Time (nDS Low to Next Time Low)
DIR Hold from nDS Inactive
nDS Low to Valid Data
nDS High to Data High Impedence
nDS Low Width
nDS High Width
nIOCS16 Output Delay from nCS Low
nIOCS16 Hold Delay from nCS High
min
max
15
10
5**
0
10
4TARB*
10
0
60
20
40**
20
40***
0****
units
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
** nCS may become active after control becomes active, but the access time (t8) will
now be 45nS measured from the leading edge of nCS.
*** t12 is measured from the latest active (valid) timing among nCS, A0-A2.
**** t13 is measured from the earliest inactive (invalid) timing among nCS, A0-A2.
Note 1: The Microcontroller typically accesses the COM20022 on every other cycle.
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
Note 2: Read cycle for Address Pointer Low/High Registers occurring after an access
to Data Register requires a minimum of 5TARB from the trailing edge of nDS to
the leading edge of the next nDS.
Note 2 is applied to an access to Data Register by DMA transfer.
Figure 8.7 - Non-Multiplexed Bus, 68XX-Like Control Signals; Read Cycle
SMSC COM20022I 3.3V Rev.C
Page 59
DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
A0-A2
VALID
t1
t2
nCS
t4
t3
DIR
t7
t5
t6
t10
nDS
t9
t8
D0-D15
VALID DATA
t12
nIOCS16
t11
Note 2
t13
VALID VALUE
CASE 2: BUSTMG pin = LOW or RBUSTMG bit = 1
Parameter
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
t13
Address Setup to nDS Active
Address Hold from nDS Inactive
nCS Setup to nDS Active
nCS Hold from nDS Inactive
DIR Setup to nDS Active
Cycle Time (nDS Low to Next Time Low)
DIR Hold from nDS Inactive
nDS Low to Valid Data
nDS High to Data High Impedence
nDS Low Width
nDS High Width
nIOCS16 Output Delay from nCS Low
nIOCS16 Hold Delay from nCS High
min
max
-5
0
-5
0
10
4TARB*+30
10
0
100
30
0****
60**
20
40***
units
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
** t8 is measured from the latest active (valid) timing among nCS, nDS, A0-A2.
*** t12 is measured from the latest active (valid) timing among nCS, A0-A2.
**** t13 is measured from the earliest inactive (invalid) timing among nCS, A0-A2.
Note 1: The Microcontroller typically accesses the COM20022 on every other cycle.
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
Note 2: Read cycle for Address Pointer Low/High Registers occurring after an access
to Data Register requires a minimum of 5TARB from the trailing edge of nDS to
the leading edge of the next nDS.
Note 2 is applied to an access to Data Register by DMA transfer.
Figure 8.8 - Non-Multiplexed Bus, 68XX-Like Control Signals; Read Cycle
Revision 03-08-07
Page 60
DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
A0-A2
VALID
t1
t2
nCS
t4
nRD
Note 3
t10
t3
t9
t8
t5
nWR
t6
t11
D0-D15
t7
Note 2
t5**
t12
VALID DATA
nIOCS16
VALID VALUE
CASE 1: BUSTMG pin = HIGH
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
Parameter
Address Setup to nWR Active
Address Hold from nWR Inactive
nCS Setup to WR Active
nCS Hold from nWR Inactive
Cycle Time (nWR
to Next
)**
Valid Data Setup to nWR High
Data Hold from nWR High
nWR Low Width
nWR High Width
nRD
to nWR Low
nIOCS16 Output Delay from nCS Low
nIOCS16 Hold Delay from nCS High
min
15
10
5
0
4TARB*
30***
10
20
20
20
max
40****
0*****
units
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
***: nCS may become active after control becomes active, but the data setup time will now
be 30 nS measured from the later of nCS falling or Valid Data available.
**** t11 is measured from the latest active (valid) timing among nCS, A0-A2.
***** t12 is measured from the earliest inactive (invalid) timing among nCS, A0-A2.
Note 1: The Microcontroller typically accesses the COM20022 on every other cycle.
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
**Note 2: Any cycle occurring after a write to the Address Pointer Low Register
requires a minimum of 4TARB from the trailing edge of nWR to the leading edge
of the next nWR.
Write cycle for Address Pointer Low Register occurring after a write to Data
Register requires a minimum of 5TARB from the trailing edge of nWR to the
leading edge of the next nWR.
Note 3: Write cycle for Address Pointer Low Register occurring after a read from Data
Register requires a minimum of 5TARB from the trailing edge of nRD to the
leading edge of nWR.
Notes 2 and 3 are applied to an access to Data Register by DMA transfer.
Figure 8.9 - Non-Multiplexed Bus, 80XX-Like Control Signals; Write Cycle
SMSC COM20022I 3.3V Rev.C
Page 61
DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
A0-A2
VALID
t1
t2
nCS
t4
nRD
Note 3
t10
t3
t9
t8
t5
nWR
t5**
Note 2
t6
t11
D0-D15
t12
t7
VALID DATA
nIOCS16
VALID VALUE
CASE 2: BUSTMG pin = LOW
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
Parameter
Address Setup to nWR Active
Address Hold from nWR Inactive
nCS Setup to WR Active
nCS Hold from nWR Inactive
Cycle Time (nWR
to Next
)**
Valid Data Setup to nWR High
Data Hold from nWR High
nWR Low Width
nWR High Width
nRD
to nWR Low
nIOCS16 Output Delay from nCS Low
nIOCS16 Hold Delay from nCS High
min
0
0
0
0
4TARB*
30
10
65
30
20
max
40****
0*****
units
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
**** t11 is measured from the latest active (valid) timing among nCS, A0-A2.
***** t12 is measured from the earliest inactive (invalid) timing among nCS, A0-A2.
The Microcontroller typically accesses the COM20022 on every other cycle.
Note 1:
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
** Note 2: Any cycle occurring after a write to Address Pointer Low Register requires a
minimum of 4TARB from the trailing edge of nWR to the leading edge of the
next nWR.
Write cycle for Address Pointer Low Register occurring after a write to Data
Register requires a minimum of 5TARB from the trailing edge of nWR to the
leading edge of the next nWR.
Write cycle for Address Pointer Low Register occurring after a read from Data
Note 3:
Register requires a minimum of 5TARB from the trailing edge of nRD to the
leading edge of nWR.
Notes 2 and 3 are applied to an access to Data Register by DMA transfer.
Figure 8.10 - Non-Multiplexed Bus, 80XX-Like Control Signals; Write Cycle
Revision 03-08-07
Page 62
DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
t12
t13
nIOCS16
VALID VALUE
A0-A2
VALID
t1
t2
nCS
t4
DIR
t3
t5
t7
t10
nDS
t8
t11
Note 2
t6**
t6
t9
VALID DATA
D0-D15
CASE 1: BUSTMG pin = HIGH
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
t13
Parameter
Address Setup to nDS Active
Address Hold from nDS Inactive
nCS Setup to nDS Active
nCS Hold from nDS Inactive
DIR Setup to nDS Active
Cycle Time (nDS
to Next Time
)**
DIR Hold from nDS Inactive
Valid Data Setup to nDS High
Data Hold from nDS High
nDS Low Width
nDS High Width
nIOCS16 Output Delay from nCS Low
nIOCS16 Hold Delay from nCS High
min
15
10
5
0
10
4TARB*
10
30***
10
20
20
max
40****
0*****
units
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
***: nCS may become active after control becomes active, but the data setup time will now
be 30 nS measured from the later of nCS falling or Valid Data available.
****: t12 is measured from the latest active (valid) timing among nCS, A0-A2.
*****: t13 is measured from the earliest inactive (invalid) timing among nCS, A0-A2.
Note 1:
The Microcontroller typically accesses the COM20022 on every other cycle.
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
**Note 2: Any cycle occurring after a write to the Address Pointer Low Register
requires a minimum of 4TARB from the trailing edge of nDS to the leading edge
of the next nDS.
Write cycle for Address Pointer Low Registers occurring after an access to
Data Register requires a minimum of 5TARB from the trailing edge of nDS to
the leading edge of the next nDS.
Note 2 is applied to an access to Data Register by DMA transfer.
Figure 8.11 - Non-Multiplexed Bus, 68XX-Like Control Signals; Write Cycle
SMSC COM20022I 3.3V Rev.C
Page 63
DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
t12
t13
nIOCS16
VALID VALUE
A0-A2
VALID
t1
t2
nCS
t4
DIR
t3
t5
t7
t10
nDS
t8
t11
Note 2
t6**
t6
t9
VALID DATA
D0-D15
CASE 2: BUSTMG pin = LOW
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
t12
t13
Parameter
Address Setup to nDS Active
Address Hold from nDS Inactive
nCS Setup to nDS Active
nCS Hold from nDS Inactive
DIR Setup to nDS Active
Cycle Time (nDS
to Next
)**
DIR Hold from nDS Inactive
Valid Data Setup to nDS High
Data Hold from nDS High
nDS Low Width
nDS High Width
nIOCS16 Output Delay from nCS Low
nIOCS16 Hold Delay from nCS High
min
0
0
0
0
10
4TARB*
10
30
10
65
30
max
40****
0*****
units
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
* TARB is the Arbitration Clock Period
TARB is identical to Topr if SLOW ARB = 0
TARB is twice Topr if SLOW ARB = 1
Topr is the period of operation clock. It depends on CKUP1 and CKUP0 bits
**** t12 is measured from the latest active (valid) timing among nCS, A0-A2.
***** t13 is measured from the earliest inactive (invalid) timing among nCS, A0-A2.
Note 1: The Microcontroller typically accesses the COM20022 on every other cycle.
Therefore, the cycle time specified in the microcontroller's datasheet
should be doubled when considering back-to-back COM20022 cycles.
**Note 2: Any cycle occurring after a write to the Address Pointer Low Register
requires a minimum of 4TARB from the trailing edge of nDS to the leading edge
of the next nDS.
Write cycle for Address Pointer Low Register occurring after an access to
Data Register requires a minimum of 5TARB from the trailing edge of nDS to
the leading edge of the next nDS.
Note 2 is applied to an access to Data Register by DMA transfer.
Figure 8.12 - Non-Multiplexed Bus, 68XX-Like Control Signals; Write Cycle
Revision 03-08-07
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DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
nTXEN
t4
t5
t2
t1
nPULSE1
LAST BIT
(400 nS BIT TIME)
t3
t2
t1
nPULSE2
t6
t8
RXIN
t7
min
Parameter
t1
t2
t3
t4
t5
t6
t7
t8
nPULSE1, nPULSE2 Pulse Width
nPULSE1, nPULSE2 Period
nPULSE1, nPULSE2 Overlap
nTXEN Low to nPULSE1 Low
Beginning of Last Bit Time to nTXEN High
RXIN Active Pulse Width
RXIN Period
RXIN Inactive Pulse Width
-10
850
250
10
typ
100
400
0
100
400
20
max
+10
950
350
units
nS
nS
nS
nS
nS
nS
nS
nS
Note: Use Only 2.5 Mbps
Figure 8.13 - Normal Mode Transmit or Receive Timing
(These signals are to and from the hybrid)
SMSC COM20022I 3.3V Rev.C
Page 65
DATASHEET
Revision 03-08-07
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
nTXEN
t1
t13
t3
nPULSE1
t2
t9
LAST BIT
(400 nS BIT TIME)
t4
t5
nPULSE2
(Internal Clk)
t8
t6
t7
t10
t12
RXIN
t11
Parameter
min
t9
t13
nPULSE2 High to nTXEN Low
nPULSE1 Pulse Width
nPULSE1 Period
nPULSE2 Low to nPULSE1 Low
nPULSE2 High Time
nPULSE2 Low Time
nPULSE2 Period
nPULSE2 High to nTXEN High
(First Rising Edge on nPULSE2 after Last Bit Time)
nTXEN Low to first nPULSE1 Low**
Beginning Last Bit Time to nTXEN High**
t10
t11
t12
RXIN Active Pulse Width
RXIN Period
RXIN Inactive Pulse Width
t1
t2
t3
t4
t5
t6
t7
t8
typ
max
-25
50
units
-25
50
nS
nS
nS
nS
nS
nS
nS
nS
650
450
750
550
nS
nS
200*
400*
-25
50
100*
100*
200*
10
200*
400*
nS
nS
nS
20
Above values are for 2.5 Mbps.
Other Data Rates are shown below.
TDR is the Data Rate Period
*t5, t6 = TDR/4
*t2, t7, t10 = TDR/2
*t3, t11 = TDR
**t9 = 47 x TDR +/- 50 nS
**t13 =
5
4
x TDR +/- 50 nS
Figure 8.14 - Backplane Mode Transmit or Receive Timing
(These signals are to and from the differential driver or the cable)
Revision 03-08-07
Page 66
DATASHEET
SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
t1
t3
t2
4.0V
50% of VDD
1.0V
XTAL1
Parameter
t1
t2
t3
t4
t5
min
Input Clock High Time
Input Clock Low Time
Input Clock Period*
Input Clock Frequency*
Frequency Accuracy*
typ
20
20
50
10
-200
max
100
20
200
units
nS
nS
nS
MHz
ppm
Note*: Input clock frequency must be 20 MHz (+-100ppm or better) to use the internal Clock Multiplier.
t4 and t5 are applied to crystal oscillaton.
Figure 8.15 - TTL Input Timing on XTAL1 Pin
t1
nRESET
nINTR
t2
Parameter
t1
t2
min
nRESET Pulse Width***
nINTR High to Next nINTR Low
EF = 0
EF = 1
typ
max
units
5TXTL*
TDR**/2
4TXTL*
Note*: TXTL is period of external XTAL oscillation frequency.
Note**: TDR is period of Data Rate (i.e. at 2.5 Mbps, TDR = 400 nS)
Note***: When the power is turned on, t1 is measured from stable XTAL
oscillation after VDD was over 4.5V.
Figure 8.16 - Reset and Interrupt Timing
SMSC COM20022I 3.3V Rev.C
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Figure 8.17 - 48 Pin TQFP Package Outline
Table 8.1 - 48 Pin TQFP Package Parameters
A
A1
A2
D
D/2
D1
E
E/2
E1
H
L
L1
e
θ
W
R1
R2
ccc
MIN
~
0.05
1.35
8.80
4.40
6.90
8.80
4.40
6.90
0.09
0.45
~
MAX
1.6
0.15
1.45
9.20
4.60
7.10
9.10
4.60
7.10
0.20
0.75
~
0
0.17
0.08
0.08
NOMINAL
~
0.10
1.40
9.00
4.50
7.00
9.00
4.50
7.00
~
0.60
1.00
0.50 Basic
~
~
~
~
7o
0.27
~
0.20
REMARK
Overall Package Height
Standoff
Body Thickness
X Span
1
/2 X Span Measure from Centerline
X body Size
Y Span
1
/2 Y Span Measure from Centerline
Y body Size
Lead Frame Thickness
Lead Foot Length from Centerline
Lead Length
Lead Pitch
Lead Foot Angle
Lead Width
Lead Shoulder Radius
Lead Foot Radius
~
~
0.08
Coplanarity (Test House)
o
Notes:
1)
Controlling Unit: millimeter
2)
Tolerance on the position of the leads is ± 0.04 mm maximum.
3)
Package body dimensions D1 and E1 do not include the mold protrusion. Maximum mold protrusion is 0.25 mm.
4)
Dimension for foot length L measured at the gauge plane 0.25 mm above the seating plane is 0.78-1.08 mm.
5)
Details of pin 1 identifier are optional but must be located within the zone indicated.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Chapter 9
Appendix A
This appendix describes the function of the NOSYNC and EF bits.
9.1
NOSYNC Bit
The NOSYNC bit controls whether or not the RAM initialization sequence requires the line to be idle by
enabling or disabling the SYNC command during initialization. It is defined as follows:
NOSYNC: Enable/Disable SYNC command during initialization. NOSYNC=0, Enable (Default): the line
has to be idle for the RAM initialization sequence to be written, NOSYNC=1, Disable: the line does not
have to be idle for the RAM initialization sequence to be written.
The following discussion describes the function of this bit:
During initialization, after the CPU writes the Node ID, the COM20022I 3V will write "D1"h data to Address
000h and Node-ID to Address 001h of its internal RAM within 3uS. These values are read as part of the
diagnostic test. If the D1 and Node-ID initialization sequence cannot be read, the initialization routine will
report it as a device diagnostic failure. These writes are controlled by a micro-program which sometimes
waits if the line is active; SYNC is the micro-program command that causes the wait. When the microprogram waits, the initial RAM write does not occur, which causes the diagnostic error. Thus in this case,
if the line is not idle, the initialization sequence may not be written, which will be reported as a device
diagnostic failure.
However, the initialization sequence and diagnostics of the COM20022I 3V should be independent of the
network status. This is accomplished through some additional logic to decode the program counter,
enabled by the NOSYNC bit. When it finds that the micro-program is in the initialization routine, it disables
the SYNC command. In this case, the initialization will not be held up by the line status.
Thus, by setting the NOSYNC bit, the line does not have to be idle for the RAM initialization sequence to
be written.
9.2
EF Bit
The EF bit controls several modifications to internal operation timing and logic. It is defined as follows:
EF: Enable/Disable the new internal operation timing and logic refinements. EF=0: (Default) Disable the
new internal operation timing (the timing is the same as in the COM20020 Rev. B); EF=1: Enable the new
internal operation timing.
The EF bit controls the following timing/logic refinements in the COM20022I 3V:
a)
Extend Interrupt Disable Time
While the interrupt is active (nINTR pin=0), the interrupt is disabled by writing the Clear Tx/Rx interrupt
and Clear Flag command and by reading the Next-ID register. This minimum disable time is changed
by the Data Rate. For example, it is 200nS at 2.5Mbps and 50nS at 10Mbps. The 50nS width will be
too short to for the Interrupt to be seen.
Setting the EF bit will change the minimum disable time to always be more than 200nS even if the
Data Rate is 10Mbps . This is done by changing the clock which is supplied to the Interrupt Disable
logic. The frequency of this clock is always 20MHz even if the data rate is 10Mbps.
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
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b)
Synchronize the Pre-Scalar Output
The Pre-Scalar is used to change the data rate. The output clock is selected by CKP3-1 bits in the
Setup1 register. The CKP3-1 bits are changed by writing the Setup1 register from outside the CPU.
It's not synchronized between the CPU and COM20022I 3V. Thus, changing the CKP2-0 timing does
not synchronize with the internal clocks of Pre-Scalar, and changing CKP2-0 may cause spike noise
to appear on the output clock line.
Setting the EF bit will include flip-flops inserted between the Setup1 register and Pre-Scalar for
synchronizing the CKP2-0 with Pre-Scalar’s internal clocks.
Never change the CKP2-0 when the data rate is over 5 Mbps. They must all be zero.
c)
Shorten The Write Interval Time To The Command Register
The COM20022I 3V limits the write interval time for continuous writing to the Command register. The
minimum interval time is changed by the Data Rate. It's 100 nS at the 2.5 Mbps and 1.6 μS at the
156.25 Kbps. This 1.6 μS is very long for CPU.
Setting the EF bit will change the clock source from OSCK clock (8 times frequency of data rate) to
XTAL clock which is not changed by the data rate, such that the minimum interval time becomes 100
nS.
d)
Eliminate The Write Prohibition Period For The Enable Tx/Rx Commands
The COM20022I 3V has a write prohibition period for writing the Enable Transmit/Receive
Commands. This period is started by the TA or RI bit (Status Reg.) returning to High. This prohibition
period is caused by setting the TA/RI bit with an internal pulse signal. It is 3.2 μS at 156.25 Kbps.
This period may be a problem when using interrupt processing. The interrupt occurs when the RI bit
returns to High. The CPU writes the next Enable Receive Command to the other page immediately.
In this case, the interval time between the interrupt and writing Command is shorter than 3.2 μS.
Setting the EF bit will cause the TA/RI bit to return to High upon release of the internal pulse signal for
setting the TA/RI bit, instead of at the start of the pulse. This is illustrated in Figure 9.1 following.
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
EF=0
Tx/Rx completed
TA/RI bit
Internal Setting Pulse
nINTR pin
prohibition period
EF=1
Tx/Rx completed
TA/RI bit
Internal Setting Pulse
nINTR pin
Figure 9.1 - Effect of the EF Bit on the TA/RI Bit
The EF bit also controls the resolution of the following issues from the COM20020 Rev B:
a)
Network MAP Generation
Tentative ID is used for generating the Network MAP, but it sometimes detects a non-existent node.
Every time the Tentative-ID register is written, the effect of the old Tentative-ID remains active for a
while, which results in an incorrect network map. It can be avoided by a carefully coded software
routine, but this requires the programmer to have deep knowledge of how the COM20022I 3V works.
Duplicate-ID is mainly used for generating the Network MAP. This has the same issue as TentativeID.
A minor logic change clears all the remaining effects of the old Tentative-ID and the old Duplicate-ID,
when the COM20022I 3V detects a write operation to Tentative-ID or Node-ID register. With this
change, programmers can use the Tentative-ID or Duplicate-ID for generating the network MAP
without any issues. This change is Enabled/Disabled by the EF bit.
b)
Mask Register Reset
The Mask register is reset by a soft reset in the COM20020 Rev. A, but is not reset in Rev. B. The
Mask register is related to the Status and Diagnostic register, so it should be reset by a soft reset.
Otherwise, every time the soft reset happens, the COM20020 Rev. B generates an unnecessary
interrupt since the status bits RI and TA are back to one by the soft reset.
This is resolved by changing the logic to reset the Mask register both by the hard reset and by the soft
reset. The soft reset is activated by the Node-ID register going to 00h or by the RESET bit going to
High in the Configuration register. This solution is Enabled/Disabled by the EF bit.
SMSC COM20022I 3.3V Rev.C
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10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
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Chapter 10 Appendix B
ISA Bus
LS688x2
AEN
nG
SA15-SA4
12 bit
Comparators
Q
P
P=Q
I/O Address Seeting (DIP Switches)
12
12
COM20022
nCS
LS245x2
A
SD15-SD0
A
16 bit Bus
Transceivers
B
D15-D0
16
16
DIR
nG
nIOR
nRD
nIOW
nWR
SA2-SA0
A2-A0
3
3
IRQm
nINTR
5V
nIOCS16
nIOCS16
DREQ
DRQn
nDACK
nDACK
TC
TC
nREFRESH
nREFEX
RESETDRV
nRESET
Schmitt-Trigger Buffer
Open-Collector Buffer
Figure 10.1 - Example of Interface of Circuit Diagram to ISA Bus
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SMSC COM20022I 3.3V Rev.C
10 Mbps ARCNET (ANSI 878.1) Controller with 2Kx8 On-Chip RAM
Datasheet
Chapter 11 Appendix C
11.1
Software Identification of the COM20022I 3V Rev B and Rev C
In order to properly write software to work with the COM20022I 3V Rev B and C it is necessary to be able to identify the
different revisions of the part.
To identify the COM20022I 3V Revision follow the following procedure:
1.
2.
Write 0x00 to Register-5
Read Register-5 Æ The value read from Register-5 must be 0x00.
3.
4.
Write 0xC0 to Register-5
Read Register-5*
* If the value read from Register-5 is 0x80 then the part is a COM20022I 3V Rev B
* If the value read from Register-5 is 0xC0 then the part is a COM20022I 3V Rev C
SMSC COM20022I 3.3V Rev.C
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Revision 03-08-07