IBM 2572 User Manual
CTI 2572
ETHERNET TCP/IP ADAPTER MODULE
TECHNICAL OVERVIEW
Version 1.1
CTI Part # 062-00156
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2572 Technical Overview Manual 032698 $25
Copyright 1993, 1998 Control Technology Inc.
All rights reserved.
This manual is published by Control Technology Inc., 5734 Middlebrook Pike, Knoxville, TN
37921. This manual contains references to brand and product names which are tradenames,
trademarks, and/or registered trademarks of Control Technology Inc. and Siemens AG. Other
references to brand and product names are tradenames, trademarks, and/or registered trademarks
of their respective holders.
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CTI 2572 Technical Overview Manual
PREFACE
This Technical Overview Manual provides an introduction to CTI 2572 Ethernet TCP/IP
Adapter and to the networking specifications used with the module. The manual is intended for
those individuals who wish to gain a fundamental understanding of the 2572, Ethernet, TCP/IP,
and SIMATIC TI505 PLC command interfaces.
This manual is organized as follows:
Chapter 1 describes the features of the 2572;
Chapter 2 provides an overview of local area network topologies;
Chapter 3 reviews Ethernet physical media and data link formats;
Chapter 4 provides an overview of higher level local area network protocols;
Chapter 5 discusses TCP/IP and related protocols
Chapter 6 covers SIMATIC TI505 command protocols.
Individuals interested in more in-depth information regarding Ethernet and TCP/IP may wish to
read one of the several excellent technical books available on the subject. These include
Internetworking with TCP/IP Vol I, II, and III by Douglas E. Comer (Prentice-Hall, 1991),
TCP/IP and Related Protocols by Uyless Black (McGraw-Hill, 1992), and The Simple Book
Book by Marshall T. Rose (Prentice Hall, 1991).
Please refer to the CTI 2572 Installation and Operation Guide for specifications and additional
information about the 2572 message interface.
CTI 2572 Technical Overview Manual
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TABLE OF CONTENTS
CHAPTER 1. INTRODUCTION..................................................................................................1
1.1 Description ...........................................................................................................................1
1.2 2572 Functions.....................................................................................................................2
CHAPTER 2. LOCAL AREA NETWORK OVERVIEW ............................................................3
2.1 Master/Slave vs. Local Area Networks................................................................................3
2.2 IEEE 802.5 (Token-Ring) ....................................................................................................4
2.3 Ethernet and IEEE 802.3......................................................................................................5
2.4 IEEE 802.4 (Token Bus)......................................................................................................6
2.5 Future Technologies.............................................................................................................6
2.6 Summary ..............................................................................................................................7
CHAPTER 3. ETHERNET OVERVIEW......................................................................................9
3.1 ISO Reference Model...........................................................................................................9
3.2 Ethernet Topologies and Media - Physical Layer...............................................................10
3.3 Ethernet Protocol - Data Link Layer ..................................................................................13
3.4 Ethernet Addresses.............................................................................................................15
3.5 Requirement for Higher Level Protocols ...........................................................................15
CHAPTER 4. NETWORK PROTOCOLS ..................................................................................17
4.1 Connectionless vs. Connection Oriented Protocols ...........................................................17
4.2 Common LAN Protocols....................................................................................................18
CHAPTER 5. TCP/IP OVERVIEW ............................................................................................21
5.1 TCP/IP Components...........................................................................................................21
5.2 Internet Protocol.................................................................................................................22
5.3 Address Resolution Protocol (ARP) ..................................................................................24
5.4 User Datagram Protocol (UDP)..........................................................................................24
5.5 Transmission Control Protocol (TCP)................................................................................25
5.6 Berkeley Sockets................................................................................................................27
5.7 2572 TCP/IP Support.........................................................................................................27
CHAPTER 6. PLC COMMAND INTERFACE..........................................................................29
6.1 Non Intelligent Terminal Protocol.......................................................................................29
6.2 Task Codes..........................................................................................................................30
CTI 2572 Technical Overview Manual
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TABLE OF FIGURES
Figure 1 CTI 2572..........................................................................................................................1
Figure 2 Token Ring Topology.......................................................................................................4
Figure 3 Ethernet Topology (Coax)...............................................................................................5
Figure 4 10Base5 (Thick Coax) Topology...................................................................................10
Figure 5 10Base2 (Thin Coax) Topology.....................................................................................10
Figure 6 10BaseT (Unshielded Twisted Pair) Topology..............................................................11
Figure 7 Fiber Optic Hub ............................................................................................................12
Figure 8 Ethernet Bridge .............................................................................................................12
Figure 9 Mixed Ethernet Media...................................................................................................13
Figure 10 802.3 Frame w/ SNAP Header....................................................................................14
Figure 11 TCP/IP Data Encapsulation........................................................................................21
Figure 12 Datagram.....................................................................................................................22
Figure 13 UDP Datagram ...........................................................................................................25
Figure 14 TCP Segment...............................................................................................................26
Figure 15 NITP Message Format ................................................................................................29
CTI 2572 Technical Overview Manual
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CHAPTER 1. INTRODUCTION
1.1 Description
The 2572 Ethernet TCP/IP Adapter is a single wide I/O module
which connects SIMATIC TI505 controllers to Ethernet networks.
Using TCP/IP (Transmission Control Protocol/ Internet Protocol),
other controllers or computers can access registers, counters, timers,
and memory locations in the PLC (Programmable Logic Controller).
Thus, the 2572 enables applications such as supervisory control, data
acquisition, and remote program download to be performed using
SIMATIC TI505 equipment over an industry standard local area
network.
The 2572 attaches to all media specified by IEEE 802.3 including
10Base5 (thick coax), 10BASE2 (thin coax), 10BaseT (unshielded
twisted pair), and FOIRL (fiber optic cable). User supplied 10BaseT
cabling can be attached directly to the 2572 via a RJ-45 connector.
Other media may be attached via the appropriate transceiver attached
to the AUI (Attachment Unit Interface) port. The AUI port may be
powered from the backplane or with an external power supply to
conserve backplane power.
In addition to the Ethernet ports, the 2572 provides two serial ports
Figure 1 CTI 2572
which can function as program ports for local or remote PLCs.
Operator interface devices, such as the CTI 5250 Access Module, or
personal computers running programming software, such as TISOFT, can access the PLC
memory via these ports. These ports operate concurrently with the Ethernet ports.
An array of diagnostic LEDs indicate operational status of the module, activity on the Ethernet
and serial ports, and the status of the Ethernet connection (link beat status, AUI active, collisions,
and 10BaseT reversed polarity).
The 2572 requires no user programming of the module. The initial baud rates of the serial ports
may be set by switches. All options are set by switches on the module or via word values set by
PLC logic.
CTI 2572 Technical Overview Manual
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1.2 2572 Functions
Server Mode
In Server Mode, the module responds to PLC commands embedded in the TCP/IP packet. The
initiating device (usually a computer or a 2572 operating in client mode) encapsulates the PLC
command in the TCP/IP protocol and transmits it to the IP address of the 2572. The 2572
retrieves the command from TCP/IP and formats a corresponding request to the PLC processor.
When the 2572 receives the response from the PLC processor, it encapsulates the response in the
TCP/IP protocol and transmits it back to the IP address which sent the initial command.
No PLC programming is required to support server mode. However, the initiating device must
encapsulate the proper command in the TCP/IP protocol and must properly process PLC
responses which the 2572 embeds in TCP/IP. Many operating systems contain support for
TCP/IP. Unix contains native TCP/IP support; IBM OS/2 and Microsoft Windows provide
optional TCP/IP support. MS DOS does not directly support TCP/IP, but several companies
offer DOS TCP/IP drivers.
Client Mode
In Client Mode, the 2572 can initiate a TCP/IP message. PLC logic is used to tell the 2572 what
to send, where to send it, and when to send it. Using 2572 Client Mode, the local PLC can read
and write memory in other remote PLCs or it can send messages to supervisory computers based
on events detected by the PLC (alarm detection, data logging, etc.). Since a 2572 can operate as
both a server and a client, multiple PLCs (each with a 2572), can participate in peer to peer
communications.
Serial Redirect
Serial Redirect is a very powerful feature which routes data received at a serial port on the
module to another node on the network. Once the serial port has been configured for the type of
service and a destination address has been established, the 2572 will encapsulate the serial port
data in TCP/IP and send it to the destination. Replies from the destination address will be routed
back to the serial port. Using Serial Redirect, devices which normally communicate with the
programming port of the PLC can access remote PLCs. For example, a PC running TISOFT
could download programs to other PLCs on the network.
2
CTI 2572 Technical Overview Manual
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