The rs232 protocol was developed in 1970 by the American Electronics Industry Association (EIA) in collaboration with Bell Systems, modem manufacturers, and computer terminal manufacturers.
Its full name is \"Technical standard for Serial binary Data Exchange Interface between Data Terminal Standby (DTE) and Data Communication Standby (DCE)\".
rs232 communication protocol disadvantages:
(1) The signal level value of the interface is high, easy to damage the chip of the interface circuit, and because it is incompatible with the TTL level, it is necessary to use a level conversion circuit to connect with the TTL circuit.
(2) The transmission rate is low, in the asynchronous transmission, the baud rate is 20Kbps; Therefore, in the CPLD development board, the comprehensive program baud rate can only be used 19200, which is also the reason.
(3) The interface uses a signal line and a signal return line to form a common ground transmission form, which is easy to produce common mode interference, so the anti-noise interference is weak.
(4) The transmission distance is limited, the maximum transmission distance standard value is 50 feet, in fact, it can only be used at about 15 meters.