Summary of Contents for Control Technology Ethernet TCP/IP Adapter Module CTI 2572
- Page 1 CTI 2572 ETHERNET TCP/IP ADAPTER MODULE TECHNICAL OVERVIEW Version 1.1 CTI Part # 062-00156 ' # ( "#' 2572 Technical Overview Manual 032698...
- Page 3 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.
- Page 5 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.
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Page 7: 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) ... - Page 9 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 ...
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Page 11: Chapter 1. Introduction
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). -
Page 12: 2572 Functions
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. -
Page 13: Chapter 2. Local Area Network Overview
CHAPTER 2. LOCAL AREA NETWORK OVERVIEW Local Area Networks (LANs) grew from the need to interconnect many intelligent devices in a non-proprietary manner. Today, the most widely used LAN standards are Token-Ring (IEEE 802.5) and Ethernet (IEEE 802.3). Token Bus (IEEE 802.4), was proposed by GM in the late 80’s as a part of the Manufacturing Automation Protocol (MAP). -
Page 14: Ieee 802.5 (Token-Ring)
On the other hand, token ring is costly (about 4 to 5 times more than Ethernet) and its technology is closely tied to proprietary IBM technology. In some situations, the ring topology of token-ring networks may not be as well suited to the factory floor as a bus topology. -
Page 15: Ethernet And Ieee 802.3
2.3 Ethernet and IEEE 802.3 Officially, "Ethernet" is the name of a CSMA/CD network developed at Xerox. It was jointly documented by Digital Equipment Corporation (DEC), Intel, and Xerox in a 1982 specification for Ethernet Version 2. This specification is commonly called Ethernet II or "Blue Book" Ethernet for the color of the specification cover. -
Page 16: Ieee 802.4 (Token Bus)
The primary disadvantage of Ethernet is that the response time is not consistent under widely varying loads. As the network loading increases above 50% , collisions occur more frequently and the network response time increases. In practice, most large busy networks use bridges to reduce the number of collisions. -
Page 17: Summary
2.6 Summary Older master/slave networks are rapidly being replaced by standard LANs which provide better performance, multi-vendor support, and integration with information networks. Of the current LAN standards, Token-Ring and Ethernet have the significant market share. Token Bus, because of the cost and complexity, has never become a major contender for the factory LAN market. In general, Ethernet offers the most cost-effective and flexible factory floor networking solution available today. -
Page 19: Chapter 3. Ethernet Overview
CHAPTER 3. ETHERNET OVERVIEW 3.1 ISO Reference Model Modern network implementations separate data communication functions into layers. Each layer performs a specific set of services and interacts with layers above and below in a well defined way. In 1984 the International Standards Organization published the Open Systems Interconnection (OSI) Reference model. -
Page 20: Ethernet Topologies And Media - Physical Layer
3.2 Ethernet Topologies and Media - Physical Layer Ethernet Version 2 and IEEE 802.3 are fully compatible at the physical level. Therefore the formal IEEE 802.3 specification is used to describe all Ethernet media. The 802.3 specification provides for a variety of topologies and media. All commonly used media operate at 10 Mb. Specified media/topology can be used interchangeably and can be intermixed on the same network. -
Page 21: Figure 6 10Baset (Unshielded Twisted Pair) Topology
Although 10Base2 cabling avoids the expense of a hub, it presents a major disadvantage for large installations. Because "T" connectors are used at each tap, there are two connections to the main cable for each node. Should a problem develop with the "T" connection, communications between stations above the connector and stations below the cable would be lost. -
Page 22: Figure 7 Fiber Optic Hub
FOIRL (Fiber Optic) Like the 10BaseT standard, the fiber optic cabling scheme uses a hub technology. Network stations are connected to the hub via point to point fiber optic connections. The fiber optic cable is attached to the network adapter using transceivers connected to the AUI port. -
Page 23: Ethernet Protocol - Data Link Layer
Mixed Media Multiple media types may be used on the same network. In larger installations it is very common for distributed 10baseT hubs to be interconnected via a fiber optic hub. The fiber optic "backbone" provides extended distance and additional noise immunity while the 10BaseT cabling provides a simple connection to nodes within a local area. -
Page 24: Figure 10 802.3 Frame W/ Snap Header
The Ethernet Version 2 standard defines the packet as follows: Ethernet Destination Address 6 bytes The type field is used to define the upper level protocol being used (e.g. TCP/IP, DEC LAT, etc.). The IEEE 802.3 specification substitutes a length field for the type field and has the following format: Ethernet Destination Address... -
Page 25: Ethernet Addresses
As you may notice, the Ethernet II format provides the Ethernet type information in 2 bytes while the 802.3 SNAP requires 8 bytes to provides this information. Consequently, most TCP/IP installations use the Ethernet II frame format. The 802.3 SNAP format is typically used only when strict 802.3 compatibility is required. -
Page 27: Chapter 4. Network Protocols
CHAPTER 4. NETWORK PROTOCOLS 4.1 Connectionless vs. Connection Oriented Protocols In most networking discussions you will find references to connectionless and connection- oriented services. The following analogy may help you understand the features and advantages of each. Connectionless Protocols Connectionless services may be compared to the standard U.S. mail. You place a letter in an envelope and mail it. -
Page 28: Common Lan Protocols
NETBUEI NETBUEI (NetBIOS Extended User Interface) is the protocol stack used by Microsoft LAN Manager and IBM LAN Server. More recently, Windows for Workgroups, a Microsoft product, uses NETBUEI. NETBUEI uses LLC (802.2) to provide both connectionless and connection-oriented services. - Page 29 IPX/SPX IPX (Internet Packet eXchange) and SPX (Sequenced Packet eXchange) are proprietary protocols used by Novell Netware. IPX is similar to Xerox’s Internet Datagram Protocol. IPX provides an unreliable connectionless transmission service. Since IPX is classified as an unreliable protocol, upper level command protocols (such as Netware Core Protocol) must provide their own delivery verification.
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Page 31: Chapter 5. Tcp/Ip Overview
CHAPTER 5. TCP/IP OVERVIEW 5.1 TCP/IP Components TCP/IP consists of a hierarchy of related protocols. Upper level protocols are encapsulated in the data structure of lower level protocols. Figure 11 TCP/IP Data Encapsulation In a typical application using the 2572, the host computer application sends PLC commands via either TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) services. -
Page 32: Internet Protocol
5.2 Internet Protocol Internet Protocol (IP) provides a basic packet delivery service. Technically, this service is defined as unreliable, connectionless, and best-effort. Unreliable means that delivery is not guaranteed by the protocol. The packet may be lost, duplicated, delayed, or delivered out of order. - Page 33 A typical IP address consists of a network ID portion and a host ID portion. The distribution of the address bytes between network ID and host ID is defined by the address class. Class A uses the first byte for the network ID and the remaining three bytes for the host ID. Class B uses two bytes for the network ID and two bytes for the host ID.
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Page 34: Address Resolution Protocol (Arp)
the datagram may actually pass through many gateways before reaching the destination network. IP has defined a comprehensive set of rules for processing datagrams. Among these specifications are the Internet Control Message Protocol (ICMP). Internet Control Message Protocol (ICMP) As described above, IP uses a best-effort method to deliver datagrams to their destination. There will be times IP cannot deliver a datagram to its destination (host system down, network congestion, etc.). -
Page 35: Transmission Control Protocol (Tcp)
UDP headers are contained in IP datagrams. Data is directed to a particular process by the use of a port number. In essence, a port is a message queue for the destination application. Certain port numbers may be universally assigned and are called well known ports. -
Page 36: Figure 14 Tcp Segment
TCP will notify both application programs. Typically one host computer (server) issues a passive open to a port, making the services available. Another host computer (client) issues an active open to initiate the connection. When the application session is complete, the connection is terminated by issuing a close to the port. TCP supports multiple connections to a single port and full duplex connections (two concurrent data streams flowing in the opposite direction). -
Page 37: Berkeley Sockets
UNIX, Berkeley Sockets were designed as an extension of the UNIX file I/O system. The equivalent sockets interface is now available under most common operating systems including IBM OS/2, Novell Netware, Microsoft Windows, and DOS (via 3rd party software). 5.7 2572 TCP/IP Support The 2572 fully supports the TCP/IP standard discussed in this chapter including UPD, TCP, ICMP, and ARP. -
Page 39: Chapter 6. Plc Command Interface
CHAPTER 6. PLC COMMAND INTERFACE 6.1 Non Intelligent Terminal Protocol As discussed in previous sections of this manual, application programs communicate with the PLC by sending messages to the 2572 encapsulated in the TCP/IP protocol. The most common message format used by SIMATIC TI505 series PLCs is the Non Intelligent Terminal Protocol. Originally developed for programming units and simple ASCII terminals, NITP is widely used by most products that access the programming port of the PLC, including PCs running TISOFT. -
Page 40: Task Codes
6.2 Task Codes As noted above the first word of the body of an NITP message contains a command. SIMATIC TI505 PLCs use a command structure known as task codes. Task codes are a set of numeric command codes which allow an external device to supervise and control the operation of the PLC.
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