【 Weak current College 】 serial technical details 】

(1) introduction
RS-232, RS-422 and RS-485 are serial data interface standard, initially by the electronic industries Association (EIA) developed and published, the publication in 1962 RS-232, named EIA-232-E, as industry standards, to ensure that the different manufacturers are compatible between products. RS-422 evolved by RS-232, it is not enough to compensate for the RS-232. To improve short-232 communicate distance, rate, low defect RS-422 defines a balanced communication interface, transfer rate up to 10Mb/s, transmission distance extension to 4000 feet (rate is lower than 100kb/s), and allow a balance between the bus connection up to 10 receivers. RS-422 is a stand-alone sent, many computer receives one-way, balance transfer specification, being named the TIA/EIA-422-A standards. To extend the application range, EIA and in 1983 has developed on the basis of RS-422 RS-485 standards, increased the number of points, bidirectional communication capability, which allows more than one transmitter is connected to the same bus, at the same time increased transmitter drive capability and conflict protection characteristics, common-mode range expanded bus, named after TIA/EIA-485-A standards. Because standard EIA recommendations are prefixed by the "RS", so in the communications industry, still accustomed to the standard RS for prefix titles.

RS-232, RS-422 and RS-485 performance parameter table:

Provides single difference RS-232RS-422RS-485 working mode differential, node 1 1 episode 1-episode 1-episode 32 10 debt collecting maximum transmission cable length 15m (20m) 1000m1000m maximum transfer rate 20Kb/S10Mb/s10Mb/s maximum driver output voltage +/-25V-0.25V ~ + 6V-7V ~ + 12V drive output signal level
(Load min) load +/-5V ~ +/-15V +/-2.0V +/-1.5V drive output signal level
(No maximum) unloaded +/-25V +/-6V +/-6V drive load impedance (Ω) 3K ~ 7K10054 slew rate (maximum) 30 V/μ s A N/N/A receiver input voltage range of +/-15V-10V ~ + 10V-7V ~ + 12V receiver input threshold +/-3V +/-200mV +/-200mV receiver input resistance (Ω) 3K ~ 7K4K (minimum) ≥ 12K drive common mode voltage
-3V ~ + 3V-1V ~ + 3V sink common mode voltage
-7V～+7V-7V～+12V
(3) Some considerations for RS-232
RS-232 commonly used three pin is 2, 3, 5. Of which 5 are ground, 2 and 3 is used to transfer data. So in actual use be used two line sequence of lines: 2, 3, 2, 3, straight and cross.

RS-232 connector can be divided into public header (all pins) and female head (full of holes).