ComputerWise -- TNET System

TNET System

CONTENTS: Introduction; Overview; Theory; Operation; Network Controller; Distribution Hubs; Gateway Devices; Terminals; Terminal Options; Diagram (37k/ pdf)

Introduction to TNET

If you have been searching for affordable shop floor data collection you need to look no further than ComputerWise's TNET system which can put interactive data entry/display terminals at each of your in-plant work stations for under $500. per station . TNET is a simple, easy-to-install system which front-ends your in-house computer and can deliver up-to-the-minute data, either key-entered or barcoded, for applications such as:

Shop floor data collection or data capture
Shop floor software
Shop floor data capture
Shop floor data collection
Factory floor data capture
Factory floor data collection
Factory data collection
Manufacturing data collection
Labor data collection
Labor tracking software
Factory data collection
Time and attendance
Records management
Work in process (WIP) tracking
Inventory and production control
Shop floor labor tracking
Production tracking.

Overview

"TNET", which stands for TransTerm NETwork, is the equipment (hardware) and interconnecting cable which together form an interactive data collection system. Software is available to integrate TNET into a variety of applications. TNET supports any of our TransTerm terminals and is controlled by the TIM1B network controller which connects to your host computer system via an RS-232 serial communications port.

Beyond the TIM1B (RS-422 communications), the network consists of TLD2 hubs and Data entry Terminals. Up to four terminals or TLD2s can be connected directly to a TIM1B. The TLD2s (Hubs) can be interspersed up to 2000 feet apart with one to six terminals connected to each TLD2. The network is interconnected with eight-conductor modular telephone cable which installs quickly and easily.

Theory

TNET is a polled network. Data is transferred bi-directionally on the network in asynchronous serial ASCII coding in accordance with a strictly defined dialogue (or "protocol") between the network controller and each of the remote terminals attached to the network. A Terminal can send the Host a "Data Block" the same time the Host sends the Terminal a "Data Block". The TIM1B has internal buffers to prevent any loss of data. The "Data Block" is simply the ID of the Terminal sending or receiving the block and the message (ASCII data).

The network electrical cabling (RS-422) consist of the two signal paths each on its own pair of conductors and a system ground. The two signal paths are either parallel adjacent paired wires (such as modular telephone cable) or twisted wire pairs with a 120 ohm characteristic impedance. This balanced connection has excellent noise rejection characteristics and is suitable for industrial environments. Cable lengths and can be up to 2000 feet without intermediate amplification. The TLD2s provide intermediate amplification, distribution, and can also remotely power Terminals (with some limitations). View a diagram representing an example TNET network.

Operation

When the user enters data at a terminal, the data is displayed until the terminal receives a "Poll" from the network controller. Upon receipt of a "Poll", the terminal transmits the message to the network controller. The network controller holds the message or transmits the message immediately to the Host (per instructions from the Host). The network controller continually "Polls" each remote terminal on the network to interrogate it for input data and also routes output messages from the Host computer to the appropriate terminal. The network controller is located within close proximity to the Host computer and will also communicate with other remote devices that are not terminals, but that emulate the TransTerm terminal's TNET protocol.

Network Controller

The TIM1B is a self-contained unit consisting of a high-speed microprocessor, data storage memory (battery backed up), and five serial communication ports. One port is RS232 compatible and connects to the Host computer (DB25). The other serial ports go out to TNET network devices and are RS-422/485 compatible (four RJ-45 connectors). The ports have user selectable baud rates from 110 - 19,200 bits per second. The TIM1B can be downloaded with a predefined sequence of prompt messages which will then automatically be placed on the displays of each of the network terminals in a fixed sequence. A Time Clock option is available for the TIM1B which provides an onboard clock to display the time of day at every station and time/date stamp incoming data. With this option, the internal buffer is increased from 32K bytes to 64K bytes.

The Host controls the rate at which incoming data is processed to prevent data from being lost under overload conditions. The format of these ASCII messages being sent between the TIM1B and the host (in both directions) consists of a three digit terminal ID number followed by the message text. These two fields are separated by a user definable delimiter code and followed by a redefinable terminator code. (See the TIM1B technical manual for further details).

Distribution Hubs

The TLD2 is a signal amplifier/distributor hub. This device has eight serial communication ports, one input and seven output. All are RS-422 compatible with RJ-45 jacks (8-conductor modular telephone jacks) The TLD2 amplifies the signal from the input port and distributes to the output ports. Typically, six of the output ports are connected to Terminals and one is connected to another remote hub, although, the output ports can all be connected to any combination of hubs and terminals.

The TLD2 can also provide a source of DC power to the attached terminal(s). A terminal powered by a TLD2 is limited to a cable length of 100 feet. A terminal connected to local AC operating power is restricted to 2000 feet. An additional power adapter is needed for a TLD2 when providing power for three or more terminals.

Gateway Devices

The TIM2B is designed to interface an RS-232 device such as a Modem or PLC with TNET. The TIM2B provides the RS-232 device an ID number on the network for bi-directional communication. The baud rate, Parity, data bits etc. can be adjusted to communicate with a wide variety of RS-232 devices. (including to serve as a docking/upload station for the TransTerm 7 & 8 portable data collectors). The TIM2B is a dual ported device with a 16K buffer. One port is RS422 compatible for network connection and the other port is serial RS-232 input/output.

Terminals

There are four models of TransTerm terminals available for use on the TNET network. These are the TransTerm 4A, 5 and 6 or 9. For a terminal to be used on the network it must be equipped with the optional RS-422 compatible TNET interface. More detail about the characteristics of each of these terminals can be found in their individual specification sheets or their owner's manual.

Terminal Options

There are several options available for the individual terminals to enhance their ability to capture data. The Barcode Interface option adds the capability to decode Code 39, Extended Code 39, Code 128, Codabar, Interleaved 2of5 and UPC/EAN/JAN symbologies from a digital wand, card reader or scanner which is plugged into the interface via a 5-pin DIN connector. The Magnetic Stripe Card reader interface option allows the reading of standard magnetically encoded credit cards and/or ID cards. The reader can be free standing or mounted to the side of the terminal enclosure. Also available is an auxiliary serial interface port for unidirectional serial data communication (or bi-directional in the case of the TT5C). The terminals are also available with electroluminescent backlights for the displays. (other options are available on selected models)