The communication speed has been improved by improving the noise resistance of the UTP (Unshielded Twisted Pair) cable used for Ethernet, and the maximum communication speed is determined according to the following categories.
■RJ45 connector specifications
The RJ45 connector used for Ethernet has the pin arrangement as shown below.
There are pins that are not used up to 100BASE, and the sending and receiving pins are fixed.
1000BASE uses all pins and does not have fixed transmit/receive pins, achieving faster communication.
■Ethernet data frame
Below are the specifications of EthernetⅡ.
＜Synchronization signal/frame start signal＞
Also called a preamble, it sends a signal indicating data synchronization and the start of a frame.
It is a repeating signal of 101010, and setting the last 2 bits to 11 means that the data has started.
＜MAC address＞
A MAC (Media Access Control) address is a unique number attached to network devices such as computers and routers.
It is expressed as 6 bytes in hexadecimal as shown below, and the first 3 bytes are OUI (Organizationally Unique Identifier), which is an identification number for each manufacturer.
The remaining 3 bytes are called UAA (Universal Administrated Address), which is a number uniquely assigned by the manufacturer.
＜type＞
Stores the type of Internet protocol (TCP/IP). ex) 0x0800 is IPv4, 0x86dd is IPv6.
＜data＞
Stores sent data. The data header stores the header of TCP/IP and the sending data protocol (ex: SMTP and HTTP).
Transmission data is 46 bytes to 1500 bytes, and when the data is less than 46 bytes, 0 is stored as dummy data, and when it is 1500 bytes or more, it is divided and sent in the next frame.
＜FCS:Frame Check Sequence＞ CRC (Cyclic Redundancy Check) is used to check whether data has been sent and received correctly.
＜IFG:Inter Frame Gap＞
Allocate 12 bytes as the frame interval size.
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