Introduction Serial Connections IP/Ethernet TABLE CONTENT TA

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Remote Serial over
Introduction Serial Connections IP/Ethernet
TABLE CONTENT
TABLE CONTENT. TABLE IMAGES. INTRODUCTION Classic Style Communication Ethernet Internet Technology Network-connect existing Devices SERIAL OVER Driver Mode Mode VARIATIONS BASIC MODES Client Mode Communication Null Modem Tunnel Modem GLOSSARY TERMS.
TABLE IMAGES
Table Content Table Images Introduction Classic Style Communication Ethernet Internet Technology Network-connect existing Devices Serial over Driver Mode Mode Variations Basic Modes. Client Mode Communication Null Modem Tunnel Modem Glossary Terms
INTRODUCTION
NetCom Devices provide support bring fashioned costly machines networks. target still have benefits those long-term devices future, combine these with benefits general spreading networking technology. combination such technologies brings additional possibilities never seen before. This document intended explain terminology, different techniques options interested persons. Also different point views functions have their topic here. described functions necessarily implemented time writing.
CLASSIC STYLE COMMUNICATION
past time many machines devices have been equipped with embedded information technology. This happened with simple sensors, huge plants machinery. these devices required some kind data connection. most cases serial interface been chosen exchange data. Especially asynchronous RS-232 became very widespread. very simple interface terms cabling, function implementation. When installations grew from single machines halls full with equipment, cabling became more difficult. limitations RS-232 could requirements. Other standards have been implemented, namely RS-422 RS-485, also family field busses. Today there variety such systems market use. Each system requirements cabling protocols. device installed, necessary search suitable connection already installed data communication systems. many situations this requires adapters serial ports computer.
Control computer Machine control application Serial function library Operating System programming interface (API, function set) serial ports Operating System drivers serial ports Computer System (ISA, PCI, Com1 RS232 Com2 RS232 Com7 RS485
Long range serial line Machine communication system
Field
Image Classical communication structure
ETHERNET INTERNET TECHNOLOGY
offices data transmission Ethernet de-facto standard. Ethernet seen some major steps development. Nowadays transmitted copper cables, optical fibres even wireless radio transmission. available speed ranges beginning Mbit/s Gbit/s. same development time reliability been improved significantly. strongest force advance usage networking been Internet technology. Internet Protocol (IP) designed transport over different data carriers. This base today networks. transport over Ethernet been implemented right from beginning. Today very well understood. connecting local network Internet, devices send data virtually everywhere world. Ethernet with tree-like structure very effective. Simple (and single) cables connect locations together, while many devices this connection same time. This technology becomes accepted also industrial environments now.
NETWORK-CONNECT EXISTING DEVICES
There movement Ethernet now. point connect already existing machines sensors Ethernet. This hard, costly even impossible. direct connection network requires modification machine. This installation additional hardware, more processing power, well special drivers. this solution specific only this machine, used other machines. Serial over offers different approach. Instead implementing Ethernet port device, device remains unchanged. Even Ethernet device communicates classic serial port. NetCom server brings controlling serial port forward machine, from computer. This NetCom server controlled from virtually everywhere. network software NetCom server operating system controlling computer hides transportation details from application programs.
Control computer
Control applications
Operating System programming interfaces, drivers libraries
Com1 RS232
Network Interface
Company network
Ethernet Switch
Internet Gateway
Ethernet Switch
Server NetCom
Machine
NetCom
Field
Image Network communication structure
Using Internet technology existing installation allows common programming interface devices stations/servers operating this environment. applications designed network directly; they IP-enabled. Those systems applications communicate with many machines computers necessary. Plus does require change hardware computer.
SERIAL OVER
Connecting serial devices over IP-networks always done same way, terms hardware installation. machine serial port, this connected device like NetCom. NetCom connects Ethernet installed near machine. When configured, accessible Applications running anywhere connect this they connect serial device. Depending type control application there different point views installation. Basically they divided into "Driver mode" "Raw-IP mode". Both modes described further this document.
DRIVER MODE
classical installation remote computers, computer built-in serial port (often named Com1). This port attached system (ISA, PCI, computer. serial connector (DB25 DB9) available case computer. long-range data transmission some special cabling even transceivers attached port computer serial device away. each controlled serial device computer another serial port (Com2, Com3, more cables serial devices. Serial over reduces this equipment drastically. additional virtual serial port installed computer, often Com3. think this Com3 serial port attached special kind "system bus". This available over network from computer. very long; reaches every location accessible this system (near serial device), there serial port. This serial port installed Com3.
Application software Operating System Drivers serial ports Driver virtual serial port Com3 Network drivers System Com1 Network Interface
Company Network (virtual system bus)
NetCom
Image Driver Mode structure
Com3
classical situation control application communicates Com1. reality this means calls some driver functions perform communication task. driver responsible perform required operations system bus. serial data sent through long cabling device. installation with NetCom behaves quite similar. application uses some driver functions perform communication tasks. driver responsible perform required operations; this time over network. driver will network drivers, this invisible (and important) application. data transferred IP-Network serial port NetCom. There available usual serial data cable device.
overall result there minimum difference between classical installation NetCom connection. only change application Com3 instead Com1. This shouldn't problem, since applications configurable. also possible install NetCom Com1. There also need change anything serial device. computer restricted serial port NetCom device. only limit virtual serial ports limit operating system. Windows this maximum serial ports, Windows 2000/XP 256. Since there expensive hardware installed computer, easy have backup redundant system, parallel. Classical connector controlled device; more interface boards more ports cable connected device Cable length limited RS-232 RS-422/485, other transceiver technology Doubled hardware costs backup systems NetCom connections through same single existing network interface Single common network cable Unlimited distance data transport TCP/IP (Internet technology) special hardware required backup systems
MODE
mode applications establish direct connection other applications. applications operate with network functions themselves, without virtual serial driver. communicate they data structure describing connection. most operating systems this structure called socket. Therefore Mode often called "Socket Mode". NetCom acts Internet server. permanently waiting incoming connections. When used driver mode, there simultaneous connections. transports control information, while other serial data.
Application serial NetCom Driver
Application network Socket library
Control NetCom
Data Com3
Server
Data NetCom
Image Driver Mode connections
Image mode connections
Mode only Data connection used. parameters serial port (speed, parity, predefined configuration. When connection comes data received sent device serial port. data received over serial port transferred connected system network. There difference access other type servers like FTP. Because NetCom acts like other Internet servers, this called Server Mode. serial device network enabled. this shall done implementation device, Ethernet port installed internal system bus. Certain drivers network IP-access necessary. Depending device this very expensive.
With NetCom device remains unchanged. seems have external system serial port, connected IP-Networks. Control Applications take profit network features. Connections devices opened demand. device accessed IP-Address symbolic name available database. Different applications different computers access device. Plus necessary install driver system. firmware serial device also enhanced. same cases direct implementation Ethernet port TCP/IP expensive. device operate known protocol HTTP over serial line. Together with NetCom this device server, ordinary browser access This convenient many customers. Driver mode Installs virtual serial ports Supports existing dedicated applications Special features Windows (and Linux) mode Does require driver Supports devices common interface Available networked operating Systems
VARIATIONS BASIC MODES
Driver mode mode fixed terms. There variations them. Different communication tasks require different settings. options NetCom targeted nearly every communication environment. Here short list sub-modes described later. Client communication Null Modem tunnel Modem
CLIENT MODE
description mode NetCom used server station. NetCom accessible network. "Listening" state waiting connection come With this connection opens transparent tunnel serial data. related Client mode function communication partners reversed. controlling computer "Listening" state, waiting incoming connections. NetCom configured establish terminate this connection special circumstances. most installations NetCom configured open connection when data arrived serial port. data transferred server computer. when data arrived specified time, connection closed.
Controlling Computer Server application NetCom
Image Client Mode
NetCom
This handy observation sensors sending data once period several minutes. connection opened NetCom, closed more data received e.g. seconds. controlling computer only needs collect data. required actively
open simultaneous connection each sensor. Nevertheless sensor data arrives real time. contrast some other products, NetCom still available Server Mode even Driver Mode, when client connection actually closed. operation mode adapts actual situation.
COMMUNICATION
connections reliable. transmission reception data guaranteed. This reduces burden secured protocols applications. However there some overhead transmitted data. When sending small packages serial data (e.g. temperature sensor) client mode, this overhead more then total amount data sent. secured like this. data send stored frame data, sent out. There guarantee delivery. data sent relatively fast. network which transports data reliable, some packet loss tolerated, then option. data sent faster, NetCom immediately free other operations; does wait computer accept data.
Controlling Computer Data Server application
Image Communication
NetCom
Since communication partners must operate same way, there difference between "Server" "Client". These phrases used application level, station offers data another consumes that. level they operate same way. this mode NetCom makes distinction about Server Client; hence named Communication.
NULL MODEM TUNNEL
This variation driver mode. NetCom communicate with each other. Data received serial port sent other device network. second NetCom data sent again over serial line. this same pair NetCom acting Server Client mode. connected such Null Modem pair also status control signals (RTS/CTS, DTR/DSR) transferred between NetCom. connection NetCom Internet operates like serial Null Modem cable. only difference fixed serial speed both sides. automatic speed detection reliable every configuration transmitted data. advantage both ends connection need operate identical serial settings. rare cases useful configuration different.
NetCom
RxD/TxD Image Null Modem tunnel
Company network
NetCom
TxD/RxD
there machine computer, with chance implement network technology, this operation mode choice. software does need change, communication still serial port. instead placing communication partners together (less than 40ft with RS232) special long range cabling drivers, this replaced NetCom. Both systems unchanged, extra cabling required.
MODEM
(Formerly named "Internet Modem"). some installations long range problem been solved using Modems. Modem installed near each controlled device/machine. controlling computer also Modem. software dials device company phone system. This computer application control many devices. With NetCom phone system replaced company network even Internet). application list phone numbers dial. These ordinary phone numbers replaced IP-Addresses NetCom controlled devices. NetCom computer establishes connection devices, thereby acting like Modem. Dialling done standard commands, there CONNECT response,
Controlling computer Modem enabled control application Com1 ATDT 12.34.56.78:2002 NetCom Company network NetCom NetCom NetCom NetCom
Image Modem Internet
NetCom
computer still controls devices. range connections extended Internet. computer control more devices than before. application unchanged.
Situation Computer running Windows Linux, existing application operating serial ports Computer TCP/IP functions, software implemented Computer must monitor several stations, amount data Computer must monitor several stations, reduce network overhead, some data loss acceptable. Computer device have network Computer network function, must control several devices
Solution Driver mode
Server Mode Client Mode Communication
Null Modem tunnel Internet Modem
GLOSSARY TERMS
APIPA: Automatic Private IP-Addressing scheme self-assign IP-Address network device. device selects address LINKLOCAL range 169.254.0.1 169.254.255.254 random. this address unused, assigns itself. Otherwise next address tested. became widespread with Windows netmask 255.255.0.0, addresses routed Internet. Automatic Receive Transmit control Special control RS485 modes. RS485 line driver transmitting must disabled (tri-stated) when device does send data. wire configuration this known data direction change, with wire called line contention. Dynamic Host Configuration Protocol service used retrieve IP-configuration from database. File Transfer Protocol common protocol access file server. HyperText Transfer Protocol protocol used browsers access server. connecting networks protocols exchange data between different networks. These information's carried global network fibres satellite links. Internet Protocol basic definitions data packages. These Internet frames stored transported embedded data frames local network.
ART:
DHCP:
FTP: HTTP:
Internet:
IP-Address:
Internet Address Internet address noted group decimal numbers. Each station Internet unique address. Some ranges reserved private networks, connected Internet. LINKLOCAL: This reserved address range private (i.e. connected Internet) networks. Designed small number stations. Used with APIPA. NAT: Network Address Translation technique have private share public IP-Address. With transport information IP-frames exchanged public data NAT-Router. Netmask: Groups stations AND-operation between IP-Address Mask important value. When stations have identical value here, they same net". Which means they communicate direct, without transmitting Router. PAT: Port Address Translation technique share public IP-Address many internal servers private addresses. target address port exchanged with values stored internal table. Mostly used together with NAT. Router: Transmits data over Internet backbone devices Internet. Routers connect networks together. side they receive data frames containing IP-data. They extract these data, send them another side; there also stored data frames second network. Typically they connect more than networks. basic task decide which route IP-data must take now.
RS-232/V.24: common serial transmission Characters sent separate bits, timing well defined. medium copper cable, using typical +/12 Volt. Each signal defined related common ground; wire signal plus GND. RS-232 point-to-point connection. RS-422: Industrial serial transmission (multidrop) transmission method with differential signals. Allows higher speed, longer cables resistive against electrical noise. RS-422 allows receivers. transmission twisted pair copper cable using differential signals. Sender receivers must share common voltage range (max. +/-7Volt difference). lines signal, plus common GND. RS-422 point-to-multipoint connection. RS-485: Industrial serial transmission (multipoint) signals cables same RS-422. transmitters tri-state. Several stations send data same lines, different times. RS-485 multipoint-to-multipoint connection. SNMP: Simple Network Management Protocol general purpose configuration system. Devices understanding SNMP configured monitored. TCP/IP: Transmission Control Program/Internet Protocol establishes connections between partners Internet. data sent IP-frames, each frame acknowledged recipient. Lost packages repeated. Software using secured transmission; delivery data guaranteed. UDP: User datagram protocol Similar data sent IP-frames. opposite there connection acknowledge recipient. transmission faster small data, data lost. Software using must handle related problems.

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