Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

28 Chapter1
Introduction
Datacommunications and Terminal Subsystem (DTS)
NOTE Direct and remote connections may be mixed on the same DTC, since its
design is modular.
A Telnet Access Card and an X.25 Network Access Card cannot be on
the same DTC 48. (Note that neither DTC/X.25 Network Access Cards
nor a Telnet Access Card may be mounted in slot 0 for DTC 48s.
On networks that are not managed by the OpenView DTC Manager,
devices connected through the DTC function as if the connection were
made through a single cable between the device and its associated
MPE/iX host system. Such DTCs (and the attached devices) can access
only their host system, and their operations are controlled by software
that is downloaded from the MPE/iX host when the DTC is powered up
or reset. The downloaded information includes configuration files that
define the devices connected to the system, and operating code to
control the functions of the DTC.
If, on the other hand, the OpenView DTC Manager is used for network
management, configuration information and controlling code for the
DTCs on the LAN are managed and downloaded by the OpenView
workstation. Offloading network management functions from the host
systems to the OpenView DTC Manager allows for much greater
flexibility in how connections can be made through a DTC. For example,
it becomes possible for a terminal connected to a single DTC to access
more than one MPE/iX or UNIX system (or both MPE/iX and UNIX
systems) on the LAN, since configuration files need no longer explicitly
define connections to a single host system.
Regardless of which type of network management is used, once the
controlling code and configuration information has been downloaded,
the DTC is ready for operation. Devices physically connected to its ports
and properly configured can then establish communication links with a
host computer.
A DTC Self-Test and an offline Self Diagnostic program are available to
diagnose any problems encountered when a DTC is powered-on or
reset.
When an MPE/iX host manages your DTCs, an online diagnostic
program, TermDSM, is available to help diagnose any problems which
may occur during DTS operation. Use of the online diagnostics as
described in detail in the Troubleshooting Terminal, Printer, and Serial
Device Connections manual.
If an OpenView workstation is part of the network, the diagnostic
functions otherwise performed through TermDSM are provided instead
by the diagnostic facilities that are a part of the OpenView DTC
Manager software. See Using the OpenView DTC Manager manual for
more information on using these facilities.