Omron R6YXC1000, User Manual, Page: 130 / 260

6
Exter
nal comm
unica
tion interf
ace
6-20
3.8.2 Glossary
■
TCP/IP
TCP/IP is a general term for a group of standard protocols for carrying out communications over the Internet around TCP
and IP protocols. Computers capable of accessing the Internet all use TCP/IP protocols.
The YRCX incorporates the TCP, IP, ICMP, ARP, and TELNET protocols of the TCP/IP protocols.
■
Ethernet
One of the network related hardware standards.
This Ethernet is a network that was developed by Xerox in the United States at the beginning of 1970s. Presently, the
Ethernet is standardized internationally as IEE802.3. According to the transmission cable type, the Ethernet is classified
into 100BASE-T2, 100BASE-T5, and 100BASE-TX, etc. The maximum cable length or the maximum number of connections
may vary depending on the classification.
The YRCX adopts the 100BASE-TX specifications.
Protocols that are generally used on the Ethernet are NetBEUI and IPX/SPX in addition to the TCP/IP protocols.
The CSMA/CD data transmission method is also the features of the Ethernet.
■
CSMA/CD (Carrier Sense Multiple Access with Collision Detection)
CSMA/CD is a method of sending signals, developed by combining a CSMA data transmission method with a transmission
error handling method called CD.
CSMA refers to joint use of one transmission cable by many devices connected over a network. CSMA is therefore a
method for checking network status beforehand and then transmitting the data after verifying that transmission is
possible.
CD is a method for handling data collisions that occur on the network. In this method, when a data collision occurs, that
data is re-transmitted after a randomly selected time period has elapsed.
Many devices can be connected to the Ethernet by using these CSMA/CD methods. However, performance cannot be
guaranteed in real-time because of transmission standby (time awaiting transmission) and retransmissions.
■
IP address
This IP address is a number unique to each device that is assigned to each device so that the numbers are not duplicated
with each other so as to identify the device on the network. (More precisely, the IP address is assigned to each network
interface since multiple network interfaces may be installed into one personal computer.) In the TCP/IP protocols, the
data transmission source or communication destination is specified by this IP address. The IP address is a 32bit-(4byte)-
numeric value. Normally, the IP address is separated 1-byte by 1-byte by a dot (".") and expressed in decimal notation.
For example, an IP address of "0xC0A80002" is expressed as "192.168.0.2".
The IP address consists of two address parts. One is a network address part that shows the address of the network's own
address. The other is a host address part that shows the address to identify each device.
N bits from the beginning of the IP address are used as a network address. Bits from the "N+1"th bit to 32th bit are used
as a host address. (The value of "N" is determined by the subnet mask.)
Host address part Network address part
IP address
1 N N+1 32
For example, when the IP address is "192.168.0.2" and the value of "N" (network length) is 24 bits, the network address
part is "192.168.0" and the host address part is "2". Generally, to express the network address, set "0" for the host address
part and describe "/" and the network length next to the address. In the example shown above, the network address is
expressed as "192.168.0.0/24".
One network can be connected with as many devices as there are addresses to identify them. However, host address bits
having all zeroes (0), or all ones (1) are reserved and so cannot be used. Therefore, in the example shown above, the host
address can identify 256 units. However, since "0" and "255" cannot be used, the maximum number of units that can be
connected is 254.
192.168.0.0/24
192.168.0.1
192.168.0.100
192.168.0.254
Max. 254 units