Communication Protocol skills

Key Points of interfaces and communication protocols: 1. How to distinguish different communication devices; 2. How to send and identify valid data on the Link; 3. How to Use the physical characteristics of the link and the signal encoding form; 4. How to transmit valid data from one end to the other; 5. How to control link traffic and exceptions

1. The key to distinguishing different communication devices is decoding, that is, allocating addresses. Whether it is simple IP address decoding of PCI or complex IP address compiling mechanisms of Ethernet and TCP/IP, the essential purpose is to identify the sender.

2. the identification of valid data on the link allows the receiver to identify the data as real data. The parallel bus protocol is generally represented by data ready signals, the packet transmission method involves the frame forming mechanism of the link layer. So in essence, parallel bus such as PCI and packet bus such as PCI-E are the same, although it seems that they do not have the data link layer, the essence is its data link layer is relatively simple.

3. Different communication protocols are implemented based on different physical media, including parallel PCB cabling (simple parallel, serDes, and source synchronization), long-distance twisted pair wires, optical fibers, and wireless connections (various frequencies) in these cases, we need to carefully examine the characteristics of the media for how information is carried on the corresponding physical media. Simple 0/1 encoding is sufficient for transmitting signals to the PCB and the traveling line. Because the media is reliable, 8B/10B encoding is required for the serDes interface. Wireless Communication also requires various coding methods, to overcome problems such as interference and signal attenuation of wireless media.

4. The transmission of valid data from one end to another involves routing and exchange. In simple protocols, both parties of communication are under one media. Therefore, this layer of function is hard to be noticed. In the Internet or ethernt, you need to use the routing switching function, because a large network needs to be layered to ensure maintainability. In some of the current Board-Level Interconnection Bus also used the exchange mechanism, such as rapdio, PCI-E, the Protocol is also very complex, in fact, its essence is to identify where data to send, the same as the PCI bus, because data is encapsulated in data packets for transmission, people like to use the exchange and routing terms.

5. Data Communication is implemented through dual transmission, which inevitably controls and manages links. This includes error control, traffic control, link maintenance initialization, and communication parameter coordination. In the parallel bus, this function is done by using several signal lines. Ready can perform throttling and error control. In the packet communication protocol, there is no out-of-band signal lines to implement these functions, therefore, the use of data packets is very complex and is determined by the characteristics of the link. In this way, Various Stream Control Frames exist.