RS-232

RS-232 er en gammel grænseflade for seriel digital datakommunikation, som blev introduceret i 1962. RS-232 muliggør lag-1 kommunikation mellem datakommunikationsudstyr (DCE) (f.eks. et modem) og dataterminaludstyr (DTE) (f.eks. en telegraf). De blev tidligere anvendt til PC tastaturer og mus.

De serielle mekaniske, elektriske og funktionelle karakteristikker (det fysiske lag) er beskrevet i:

ITU-T V.24, V.28^[2]
RS-232-C (Recommended Standard 232), 1969^[3]
TIA^[4] (EIA-232), TIA-232^[5]

Herefter benævnt RS-232.

I 1960'erne (og før) var elektrisk digital logik dyr, pga. de mange diskrete komponenter, der skulle til for implementere de funktioner man havde brug for. Det er nok grunden til at en RS-232 grænseflades mange out-of-band-signaler. En RS-232 har to serielle simplex forbindelser (tilsammen typisk full-duplex):

Lederen TxD (og stel, jord) som sender data til den anden ende.
Lederen RxD (og stel, jord) som modtager data fra den anden ende.

Herudover haves mange dedikerede signaler:

Request To Send (RTS)
Ready To Receive (RTR)
Clear To Send (CTS)
Data Terminal Ready (DTR)
Data Set Ready (DSR)
Data Carrier Detect (DCD)
Ring Indicator (RI)

Eventuelt dedikerede synkroniseringssignaler:

Send timing (ST)
Clock signal, transmitter timing (TT)

^ CT-1024 Terminal System Kit Arkiveret 3. juli 2008 hos Wayback Machine Citat: "...The baud rate or speed at which the serial data is transmitted or received, is 110 baud, or if the optional parts are installed, 110, 150, 300, 600 and 1200 baud...The input/output connections to the interface are RS-232 compatible..."
^ ITU-T Recommendations: V Series (kan frit downloades)
^ Electronics Industries Association, "EIA Standard RS-232-C Interface Between Data Terminal Equipment and Data Communication Equipment Employing Serial Data Interchange", August 1969, reprinted in Telebyte Technology Data Communication Library, Greenlawn NY, 1985, no ISBN
^ Telecommunications Industry Association (TIA), Electronic Industries Alliance (EIA)
^ interfacebus.com: EIA-232 Bus

[1] CT-1024 Terminal System Kit Arkiveret 3. juli 2008 hos Wayback Machine Citat: "...The baud rate or speed at which the serial data is transmitted or received, is 110 baud, or if the optional parts are installed, 110, 150, 300, 600 and 1200 baud...The input/output connections to the interface are RS-232 compatible..."

[2] ITU-T Recommendations: V Series (kan frit downloades)

[3] Electronics Industries Association, "EIA Standard RS-232-C Interface Between Data Terminal Equipment and Data Communication Equipment Employing Serial Data Interchange", August 1969, reprinted in Telebyte Technology Data Communication Library, Greenlawn NY, 1985, no ISBN

[4] Telecommunications Industry Association (TIA), Electronic Industries Alliance (EIA)

[5] terfacebus.com: EIA-232 Bus

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RS-232

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