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EIA-423 (also RS-423 ) is an interface standard for wired asymmetrical serial data transmission . EIA-423 is specified in "Electrical Characteristics of Unbalanced Voltage Digital Interface Circuits (ANSI / TIA / EIA-423-B-1996) (R2001)" by the North American ANSI .

EIA-423 has a similar structure to EIA-232 . It corresponds to the international ITU-T standard X.26 , which is identical to V.10 . X.26 defines the electrical properties for unbalanced lines at the interface of data terminal equipment (DTE) and data transmission equipment (DÜE). In contrast to the EIA-232 standard, in which there is a bidirectional point-to-point connection between two participants, EIA-423 defines a unidirectional connection between a transmitter and up to 10 receivers.

Since the interface is based on EIA-232, the same restrictions apply. Due to the high voltage of the NRZ transmission of −3.6 ... −6 V for logic 1 and + 3.6 ... + 6 V for logic 0, no terminating resistor (corresponding to the characteristic impedance) is required here. As with EIA-232, the transmission is asymmetrical with respect to ground . Instead of the EIA-232, a differential receiver is used as the receiver, as in the EIA-422 , with its specific threshold of 200 mV.

A maximum cable length of 1200 m (corresponding to 4000 feet) at 1 kBaud or 15 m at 100 kBaud is defined. Due to the differential design, this is somewhat better than with EIA-232, which originally stopped at 20 kBaud.

In order to minimize the crosstalk problem mentioned with EIA-232, with EIA-423 each data or control / message line has its own return line, similar to EIA-422. However, it is not a real differential symmetrical (balanced) transmission, since all return conductors have ground potential. Due to this fact, this standard has not found widespread use, because EIA-422 is much more immune to interference with the same effort.

The ITU-T recommendation X.27 corresponds to X.26 with the difference that the voltage levels are "balanced", ie symmetrical to ground. It is identical to V.11 .

General information about interfaces, parameters or properties can be read with serial data transmission .

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