LG GLOFA-GM Series User Manual page 17

Chapter 2 Definition of terms
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) and 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 transferring for a second. Generally, one character is 1Byte (8Bits), so CPS is the number of byte
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 transfer data into the defined length and adds a header that presents the opposite
addresses (station No., etc.) into it.
8) Port
Port is meant to be the part of the data process devices 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 only 1 : 1 communication is available, and the specifications which recover this disadvantage
are RS-422 and RS-485.
10) RS-422/RS-485
As one of the serial transmission specifications, its transfer length is long and multi (1 : N) connections are
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
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