Envoy ACP/XF Application Programming Manual

Glossary
EnvoyACP/XF Application Programming Manual–132179
Glossary-2
CONFTEXT
host-resident communication processes. CLIP software implements the specific
communications protocols, such as SDLC or HDLC.
CONFTEXT. The main configuration file that contains all the hardware descriptions
applicable to your Tandem system.
control field. The field following the address field in a bit-synchronous frame. It contains
bit-encoded commands and responses and can also contain frame sequence numbers.
The contents of the control field indicate whether the frame has an information,
supervisory, or unnumbered format. Generally, this field is 1-octet long; however, in
extended mode, the control field can be 2-octets long.
CRC. Cyclical Redundancy Check. A technique for checking the validity of a multiple-byte
block of data. If one CRC does not match that previously generated, an error exists
somewhere within the block of data. See also frame check sequence.
CTS. Clear To Send. A signal that comes from a modem, indicating to the computer
equipment that the modem is ready to accept data for transmission.
Data link. In SNA, the combination of the link connection and the link stations joining two
adjacent network nodes.
DCE. Data Circuit Terminating Equipment. DCE generally refers to the modem to which a
terminal or host computer (called the DTE) is connected.
DSR. Data Set Ready. A signal coming from a modem that usually indicates to the computer
equipment that the modem is powered on.
DTE. Data-terminal Equipment. DTE is the terminal or host computer to which a modem
(called the DCE) is connected.
extended control field. An optional control field length of 2 octets. See control field.
EBCDIC. Extended Binary-coded Decimal Interchange Code. A method of coding data
designed for synchronous use. It consists of 8 bits of data with no parity bit. There are
256 standard characters.
FCS. Frame Checking Sequence. The field in a bit-synchronous frame that contains the
cyclic redundancy check (CRC) value for the frame, used to verify correct data. It is a
16-bit field, immediately preceding the ending flag for the frame.
flag. A unique field found at the beginning and end of bit-synchronous frames, used for
synchronization and transparency control. Always set to the hexadecimal value 7E
(01111110).
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, and frame-check sequence and closing flag.