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4.6 Parameter Setup Request
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4.6 Parameter Setup Request
This section describes the procedure for EN311 parameter setup in the EN311 from an S
controller user program. The EN311 parameters consist of the following:
(1) Local station IP address
(2) UDP port number for computer link/PC link transmission
Here we first describe the IP address, subnet mask, and port number, which are the
parameters required for TCP/IP and UDP/IP transmission.
(1) IP address
The IP address is the address that specifies a particular node (station) when
transmitted data using the IP (Internet protocol). Therefore IP addresses must be set
and managed so that they are not duplicated. The following presents an overview of
IP addresses.
(a) IP address format
An address consists of a network address and a host address. The network
address is an address that specifies a particular network, and the host address is
an address that specifies a particular node (station) on that network. The same
network address must be assigned to all nodes (stations) on the same (i.e., any
given) network.
An IP address is a 32-bit data item. IP addresses are written as the decimal
values of each byte in the 32-bit datum, with the decimal values separated by
dots.
Example:11000000 00000000 00000000 00000001
→
192.0.0.1
IP addresses are divided into five classes, A through C, according to how many
bits in the 32-bit value are used as the network address (The networking
standards also define classes D and E, but the EN311 does not support them).
Figure 4-3 shows the classes A though C.
Figure 4-3 IP Address Class Divisions
In this system, networks with a large number of connected nodes use class A addresses
and networks with s small number of connected nodes use class C addresses. Class B
addresses are used for networks that fall between classes A and C. Expressed in
decimal, the first byte of the class A through C networks will be: 0 to 127 for class A, 128
to 191 for class B, and 192 to 223 for class C.
0 8 16 24 31
Class A 0 Network: 7 bits Host: 24 bits
↑
127 values
↑
16,777,214 values
Class B 1 0 Network: 14 bits Host: 16 bits
↑
16384 values
↑
65534 values
Class C 1 1 0 Network: 21 bits Host: 8 bits
↑
2,097,152 values
↑
254 values