6100 ADCCP Programming Manual

Glossary
Glossary–4 069225 Tandem Computers Incorporated
information field. The field in a bit-synchronous frame that contains data or additional
control information. If present, the information field follows the control field and
varies in length.
information frame. A frame format used to pass data between two stations.
LIM. See line interface module (LIM).
line interface module (LIM). The actual connection to the communications line. It
provides the physical and electrical interface to the outside world. The LIM is part of
the line interface unit (LIU) in a 6100 /3650 subsystem.
line interface unit (LIU). A component of the 6100/3650 subsystem. Each LIU supports a
single communications line. There can be up to 15 LIUs in a 6100 subsystem. Each
LIU consists of two parts: a communications line interface processor (CLIP) and a line
interface module (LIM). The LIU is dual-ported to allow it to communicate through
either of the communications interface units (CIUs), providing fault tolerance. (The
LIU does not communicate though both CIUs simultaneously.) See also
communications line interface processor (CLIP) and line interface module (LIM).
LIU. See line interface unit.
multipoint. A data-link configuration in which one station is designated as the
supervisor and controls all communications over the link. The other stations are
designated as tributaries.
nonswitched. A line configuration that provides a permanent path between two
stations. This path can be a privately owned cable or a dedicated path leased from a
common carrier. It is generally a leased line. Contrast with switched.
Normal Response Mode (NRM). A mode of communications within the ADCCP protocol
whereby a secondary station can transmit data only after a request from the primary
station. This mode of operation is also used by synchronous data-link control (SDLC).
NRM. See Normal Response Mode (NRM).
octet. A term used with bit-synchronous frame format. An octet is equivalent to 8 bits
or 1 byte.
path. The route between a specified line interface unit (LIU) and a CPU. Each LIU has
a primary path (Path A) and an alternate path (Path B), both of which are assigned to
different communications interface units (CIUs). The primary and alternate paths
provide fault tolerance if a CIU fails. At system generation, a group of lines in a 6100
CSS can be assigned to each path.
point-to-point. A non-multidropped, unshared data-link configuration between two
stations. This configuration can exist between a primary and a secondary station or
between two combined stations.
primary. In an SDLC or ADCCP-NRM configuration, the primary station initiates a
data transfer and is in control during the exchange of messages. It notifies each
secondary link station when the station can transmit data and when the station should
expect to receive data. See also secondary.