Local Asynchronous Communication

1. Requirements for asynchronous communication: One-Step communication means that the sender and receiver do not need to coordinate before sending data (both parties do not synchronize data before each transmission ). The keyboard in life follows such asynchronous communication.

2. power signal sending Bit String: encode the data with small current ~ Negative Voltage indicates bit 1, positive voltage indicates bit 0 (this is the simplest Electronic Communication System)

3. Communication Standards:

Voltage Transmission data must comply with the standards specified by the EIA (Electronics Industry Association). This is the most widely accepted standard ~ Transmit characters on a copper wire between a computer and a modem, keyboard, or terminal.

EIA standard RS-232-C detailed specifications for physical connections and electrical equipment (Provision for 7-character transmission)

The RS-232-C defines the Serial Asynchronous communication, that is, the data is transmitted along with one digit on the wire and the transmission process of each character is asynchronous. Note: Once a character is transmitted, the sending hardware sends all the characters one by one at a time. There may be a delay between the characters but no delay between the characters.

The RS-232 first transmits an additional bit value 0 as the start bit before the characters are transmitted, and at least one stop bit (idle time) after each character is transmitted, the time for each bit is exactly the same.

(The above content is summarized in computer networks and the Internet ~ I am a newbie to computer networks ~ If something is wrong, you are welcome to criticize and correct it ~ )