HP 3000 Manuals

Troubleshooting Terminal, Printer, and Serial Device Connections

Distributed Terminal Subsystem (DTS) 

With the exception of the system console which has its own access port,
all asynchronous serial devices can be connected to 900 Series HP 3000
computers through the Distributed Terminal Subsystem (DTS). DTS is made
up of all of the Datacommunications and Terminal Controllers connected to
the system, a LAN Interface Card, the LAN cable and the host software
that controls all the related DTS hardware.

Datacommunication and Terminal Controller 

The Datacommunications and Terminal Controller (DTC) provides the
connection between asynchronous devices and the 900 Series HP 3000 family
of computers.  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 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 DTC can provide connections for up to 48 local devices, 36 remote
devices using modems, or a combination of both.  Local and remote
connections can be mixed on the same DTC, since its design is modular.
Each DTC provides six slots, each of which can contain one of the
following connector cards:

 *  Eight 3-pin RS-232-C local connections.

 *  Eight 5-pin RS-422 local connections.

 *  Six 25-pin RS-232-C modem connections.

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 Getting Started with the DTC for more
information on host-based management and PC-based management.

TermDSM can be used only to troubleshoot connections on systems that use
host-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.

LAN Interface Card (LANIC) 

Every computer in the 900 Series HP 3000 family has a LAN Interface Card
(LANIC) as part of its hardware.  This card is located in the System
Processing Unit (SPU) and enables the system to communicate with
asynchronous devices via the LAN by providing the basic connection
between the computer and the LAN.

Datacommunications and Terminal Controllers are connected to the system
by a Local Area Network (LAN), over coaxial cable which conforms to the
IEEE 802.3 standard.  Hewlett-Packard provides two versions of this
cable, ThinLAN and ThickLAN, each provides certain specific advantages to
the user.

Each DTC has a unique LAN address which is made known to the system
during configuration.  Also referred to as the node address or the
station address, it serves to identify the DTC as a node on the LAN. Keep
in mind, however, that while DTCs are treated as nodes for the purpose of
configuration, they are not true nodes.  DTCs are dedicated communication
devices; they are not self-contained, general-purpose computer systems.

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 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 1-2 shows a ThickLAN configuration.


          Figure 1-3.  ThickLAN 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 XL operating system.  The software is included with the MPE XL
Fundamental Operating System (FOS).

The MPE XL 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.

MPE/iX 5.0 Documentation