AM3270/TR3271 Reference Manual

Glossary
086705 Tandem Computers Incorporated Glossary–1
3650/6100 family controller. Programmable controller, such as the 6101/6110 or
3605/6105, that has the following characteristics:
6100 CSS architecture
Programmable, down-loaded logic
Multiple protocol support
Single operations interface (fully reconfigurable online)
Dual or single input/output paths
Hardware resides in system, input/output cabinet, or standalone cabinet
6100 communications subsystem (CSS). A communications subsystem connected to the
Tandem channel composed of multiple microprocessors. The subsystem provides
lower-level communications protocol support by downloading software into the
microprocessors.
access method. A high-level I/O process that allows applications running on a
Tandem system to communicate with other systems or devices.
AM3270. A device-specific access method. A protocol that allows Tandem application
programs to directly access individual 3270-compatible devices connected to a
nonswitched, byte-synchronous, multipoint communications line.
ASCII. American National Standard Code for Information Interchange. A method of
coding data, consisting of seven bits for each character plus a parity bit. Designed for
synchronous or asynchronous use, the code has 128 standard characters.
asynchronous. Also called “start-stop” transmission. Time intervals between
transmitted characters may be of unequal length. Transmission is controlled by start
and stop elements at the beginning and end of each character.
bit. Binary Digit. The smallest unit of information in a binary system.
bit-synchronous. Bit-oriented block-mode protocols, such as the High-Level Data Link
Control (HDLC) protocol, which are independent of a specific code set, and do not
require reserved characters. Bit-synchronous protocols allow full-duplex
transmission, and do not require the volume of ACK/NAK transmissions required by
bisync protocols.
byte. A binary-element string that is treated as a unit. Most commonly, a six-, seven-,
or eight-bit unit.
byte-synchronous. Also called “bisync,” “bisynchronous,” or “BSC.” A method of data
transmission in which embedded control characters (rather than clock or speed
parameters) control data transmission on a link. In a block-mode terminal network,
the terminals send complete messages, rather than the character-by-character
transmission of an asynchronous protocol. Bisync protocols are limited to half-duplex
(or one-way on full-duplex) transmission.
CAP. Communications Access Process. A CAP is very similar to an Input Output
Process (IOP). A CAP works in coordination with a 3650/6100 family controller, while
an IOP—strictly speaking—works with regular (non-3650/6100 family) controllers.