Transmissions

asynchronous streaming

This transmission consists of avoiding the timing problem by sending interrupted strings of bits that are not very long. Each character is treated independently, that is, it is sent character by character, said character can have a length of 5 to 8 bits. Each character has a start bit that alerts the receiver about the arrival of the character and corresponds to the 'value 0', after this are the least significant bits and between the most significant bits is placed the parity bit used by the receiver to error detection, and finally the stop element that corresponds to 'binary 1' is found.

The timing or synchronization must be maintained for the duration of the character as the receiver has the opportunity to resynchronize at the beginning of each new character. This asynchronous transmission is simple and cheap, although it requires 2 or 3 extra bits for each character.

This technique may not work correctly for long data blocks because the clock might get out of sync. To avoid this, synchronous transmission is used.

Synchronous Transmission

In this transmission, it is sent in blocks of bits (of great length) as a stationary chain without using a start or stop code. To prevent desynchronization between the sender and receiver, their clocks must be synchronized in some way.

  1. One possibility may be to provide the clock signal via a separate line. (one of the ends will regularly send a pulse of short duration and the other end will use this signal as a clock, this technique works at short distances since synchronization errors can appear at long distances).

  2. The other alternative is to include the timing information in the data signal itself.

In synchronous transmission, an additional synchronization level is also required so that the receiver can determine where the called beginning is. preamble and the end called final. In addition to these bits, other bits that are used in link control procedures will be included.

These data blocks form a frame that is the data plus the preamble, plus the final bits along with the control information, which will depend on the link control procedure used.