The network of synchronous transmission and asynchronous transfer a lot of articles, various explanations have shown a lot, but after reading a bit confused, after all, of course, in order to truly understand these concepts thoroughly professional, the best way or find embodies these concepts in practice.
Although synchronous transmission and asynchronous transfer are two entirely different way from the name of view, but you know, their purpose is the same, in fact, bit synchronization of actions they are carrying out, only a selected destroy Huanglong, and another is circuitous combat. So first of all it should be clear a thought, if you want to understand these two methods as long as they understand how to synchronize it.
Asynchronous communication:
Recipient asynchronous communication does not know when the data will arrive, sending and receiving sides can have their own clock. Time interval may be sent by the sender unevenness, the receiver is implemented with the aid of information for synchronization start and stop bits of data. Such transmission is usually small packet, such as a character as a set, with start and stop bits for this group. Therefore the efficiency of this transmission is relatively low, after a lot of additional auxiliary bit is added as a load, often used in low-speed transmission.
For example, our keyboard presses a button to send a character signal, asynchronous transmission mechanism will assist the synchronization information before and after it with the help us to identify the recipient which key was pressed. Because we percussion rhythm keyboard is not fixed, so asynchronous it is a very appropriate way.
Synchronous communication:
Synchronous communication parties using the same clock frequency, which is asynchronous as compared to larger packets, referred to as a data frame through a unique bit string as start and stop identifier. To the sender transmits data to a fixed rhythm, and the receiver to be always ready to receive data, to identify the preamble of the received data is about to begin. Synchronization in this manner because the packet is large, a long data bit will have additional auxiliary load, therefore more efficient, is more suitable for a high transmission speed requirements, of course, such communication timing requirements are also higher.
In summary, the asynchronous transfer is in fact re-synchronize the data before and after the start and stop character code, make up for their lack of attention not just concentrated; and synchronous mode is a good student rules, always on standby ready to work. Asynchronous is throw you out a content, relying on each other before and he could smell the contents found it strange in the crowd, to keep down the content; the other is synchronized at a time waiting for orders to release you, I want you to tell each other send oh, and then the two sides hit it off.
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Original: https: //blog.csdn.net/RhythmWANG/article/details/68066584
