6100 ADCCP Programming Manual

Glossary
069225 Tandem Computers Incorporated Glossary–3
data-terminal equipment (DTE). DTE is the terminal or host computer to which a modem
(called the data-terminal equipment, or DCE) is connected.
DCD. See data carrier detect (DCD).
DCE. See data-circuit terminating equipment (DCE.).
DISC. See disconnect (DISC).
disconnect (DISC). A mode-setting command used to inform the addressed
secondary/combined station that the transmitting primary/combined station is
suspending operation with the secondary/combined station.
DSR.. See Data set ready (DSR).
EBCDIC. See Extended binary-coded decimal interchange code (EBCDIC).
exchange identification command. A command used to cause the addressed secondary or
combined station to report its station identification.
Extended binary-coded decimal interchange code (EBCDIC). A method of coding data
designed for synchronous use. It consists of 8 bits of data with no parity bit. EBCDIC
has 256 standard characters.
FCS. See frame-checking sequence (FCS).
flag. For frame formats, the flag is a unique field found at the beginning and end of bit-
synchronous frames. The flag is used for synchronization and transparency control.
The value of the flag is always set to the hexadecimal value 7E (01111110).
frame reject (FRMR). In ADCCP, a recovery response used to report an error condition
that is not recoverable by retransmission of the identical frame.
frame-checking sequence (FCS). The field in a bit-synchronous frame that contains the
cyclical redundancy check (CRC) value for the frame. The CRC is used to verify
correct data and is a 16-bit field immediately preceding the ending flag for the frame.
frame. The basic transmission unit within a bit-synchronous communications
environment. Frames are made up of the following fields: beginning flag, address
field, control field, information field, frame-check sequence, and closing flag.
FRMR. See frame reject (FRMR).
full duplex. A method of serial communications in which the data flow between two
points can occur in both directions simultaneously.
Guardian 90 operating system. The main Tandem operating system.
half duplex. A method of serial communications in which the data flow between two
points can occur in only one direction at a time.
HDLC. See High-level Data Link Control (HDLC).
High-level Data Link Control (HDLC). A bit-synchronized data communications protocol
that uses Asynchronous Balanced Mode (ABM) communications between stations.
See also Asynchronous Balanced Mode (ABM).
I-frame. See information frame.