Appendix 1 Definition of Terms
A-4
(4) Protocol
This is communication rule established in relation between the transmission side and the receiving
side of information in order to send and accept information between two computers/terminals or more
without error, effectively, and reliably. In general, this specifies call establishment, connection,
structure of message exchange form, re-transmission of error message, procedure of line inversion,
and character synchronization between terminals, etc.
(5) BPS(Bits Per Second)와 CPS(Characters Per Second)
BPS is a unit of transfer rate that represents how many bits are transferred per second. CPS is the
number of the characters transferred for a second. Generally, one character is 1Byte (8Bits), so CPS
is the number of bytes which can be transferred per second.
(6) Node
Node is a term that means the connected nodes of the data in the network tree structure, generally
network is composed of a great number of nodes, and is also expressed as the station number.
(7) Packet
Packet, a compound term of package and bucket used for packet exchange type to send information
as divided in a unit of packet, separates transferred data into the defined length to add a header that
presents the correspondent addresses (station No., etc.) thereto.
(8) Port
Port is meant to be the part of the data process device which sends or receives the data from a
remote control terminal in data communications, but in Cnet serial communication is meant to be the
RS-232C or RS-422 port.
(9) RS-232C
RS-232C is the interface to link a modem with a terminal and to link a modem with a computer, and
is also the serial communications specification established by EIA according to the recommendations
of the CCITT. This is also used to link the null modem directly as well as the modem linkage. The
disadvantage is that the transfer length is short and that only 1 : 1 communication is available, and
the specifications which have overcome this disadvantage are RS-422 and RS-485.
(10) RS-422/RS-485
As one of the serial transmission specifications, its transferring length is long with 1 : N connection
available compared to RS-232C. The difference of these two specifications is that RS-422 uses 4
signals of TX(+), TX(-), RX(+) and RX(-), while RS-485 has 2 signals of (+) & (-), where data is sent
and received through the same signal line. Accordingly, RS-422 executes the full-duplex type of
communication and RS-485 executes the half-duplex type of communication.
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