Datacommunications and Terminal Subsystem (DTS)

Datacommunications and Terminal Controller

The Datacommunications and Terminal Controller (DTC) provides the connection between asynchronous devices and the HP 3000 Series 900 family of computers. The DTC can house an X.25 Network Access Card to provide connections for nailed PAD-connected terminals and printers. Also, a DTC containing a Telnet Access Card can provide Telnet connections to an HP 9000 or other ARPA machine via Telnet/iX.

The DTC is housed in its own box, outside the system cabinet. This alleviates system limitations which are based on cabinet space considerations, and allows flexibility in the layout of terminal cables. Figure 1-1 “Datacommunications and Terminal Controller”represents the location of the DTCs in relation to the system, the LAN, and the terminals and printers connected to the system through the DTCs.

Figure 1-1 Datacommunications and Terminal Controller

Each HP 2345B DTC (DTC 48) can provide connections for up to 48 local devices, 36 remote devices using modems, or a combination of both. For the DTC 48, up to three of the DTC's slots can contain a DTC/X.25 Network Access card. This card provides access to X.25 networks, and can be used to connect asynchronous devices through PAD connections. Alternatively, a single Telnet Access Card per DTC can be used to access MPE/iX systems from ARPA systems.

Each DTC 48 provides six slots, each of which can contain one of the following connector cards:

Each DTC 72MX can provide connections for up to 72 local and remote devices. Local and remote connections can be mixed on the same DTC, since its design is modular. Each DTC 72MX provides four slots, one slot for the LAN card, and three slots each of which can contain one of the following connector cards:

The DTC 16 contains three slots. The first two slots and only the first two slots (card #0 and card #1) can contain direct connect or modem cards. The third slot (card #2) can contain only a DTC/X.25 Network Access Card.

Each DTC 16iX and DTC 16MX can provide RS-232 or RS-423 port connections for up to 16 asynchronous devices. They both have two port connectors built directly into their backplanes, each of which can be connected to a distribution panel which allows either all direct connections or all modem connections. The DTC 16iX does not support ARPA Telnet or X.25 connections. The DTC 16MX provides AFCP connections for the HP 3000 environment and telnet connections for the ARPA environment; it does not support X.25 connections for wide area networking. The DTC 16MX managed by an MPE/iX host is limited to identical functionality as the DTC 16iX.

The DTC is controlled by software that is downloaded by its host system at boot time or by the OpenView Windows Workstation, depending on the type of management used. Systems can use either host-based management or PC-based management. Refer to Configuring Systems for Terminals, Printers and Other Serial Devices for more information on host-based management and PC-based management.

The downloaded software includes DTC operating code and configuration information. Once the software is downloaded, the DTC is ready for operation. Devices physically connected to its ports and properly configured can establish communications links with the host computer.

You can troubleshoot connections with TermDSM only on systems that use host-based management. Troubleshooting for PC-based management is covered in Using HP OpenView DTC Manager.

ThinLAN Connection

LAN cable is available in two versions. The first, ThinLAN (Type 10 BASE 2), is available in connection lengths of up to 185 meters (555 feet), and provides an economical solution where DTCs are located in close proximity to their computer system.

ThinLAN is a flexible cable which is easy to install, and can be bent around objects to accommodate its use in confined areas. ThinLAN is connected to the computer through a ThinMau (Medium Attachment Unit), with a small BNC T-connector used to connect each DTC to the LAN. You can connect up to three segments of the cable with two repeaters, thus extending the length of the LAN 555 meters. Figure 1-2 “ThinLAN Configuration” shows a configuration using ThinLAN.

Figure 1-2 ThinLAN Configuration

ThickLAN Connection

The second version of the LAN cable, ThickLAN (Type 10 BASE 5) offers maximum connection lengths of up to 500 meters (1600 feet), and supports up to 100 nodes. Each node on the LAN is connected through a Medium Attachment Unit (MAU). An Attachment Unit Interface (AUI) cable runs between each node and its MAU, as well as between the host computer and its MAU. You can connect up to three segments of ThickLAN cable with two repeaters, thus extending the length of the LAN to 1500 meters. Figure 1-3 “ThickLAN Configuration” shows a ThickLAN configuration.

Figure 1-3 ThickLAN Configuration

10Base-T

Figure 1-4 “10Base-T Configuration” shows that 10Base-T is a star topology and offers a third way to lay out your Ethernet network. 10Base-T offers maximum connection lengths of up to 200 meters of unshielded twisted pair per segment and supports up to 12 workstations per HUB. You can connect multiple HUBs to the LAN with an Ethernet performance of 10 Mbps.

Figure 1-4 10Base-T Configuration

ASC Software

The Asynchronous Serial Communications (ASC) software controls the DTS hardware. It provides the interface between the IEEE 802.3 LAN and the MPE/iX operating system. The software is included with the MPE/iX Fundamental Operating System (FOS).

The MPE/iX system tracks all of the devices connected to it by means of configuration files. The network configuration information necessary to initialize and control the DTS resides in a special configuration file. This file is created through the Node Management Configuration Manager (NMMGR). Configuring Systems for Terminals, Printers, and Other Serial Devices provides a detailed discussion of the configuration process.