RS-423

RS423
Standard	EIA RS-423
Physical Media	Group of copper cables
Network Topology	Point-to-point, Multi-dropped
Maximum Devices	10 (1 driver & 10 receivers)
Maximum Distance	1200 meters (4000 feet)
Mode of Operation	Single-ended (unbalanced)
Maximum Baud Rate	Up to 100kbit/s
Voltage Levels	-6V to +6V (maximum)
Mark(1)	-4V to -6V
Space(0)	+4V to +6V
Available Signals	Tx, Rx, GND
Connector types	Not specified

RS-423, also known as TIA/EIA-423, is a technical standard originated by the Electronic Industries Alliance that specifies electrical characteristics of a digital signaling circuit. Although it was originally intended as a successor to RS-232C offering greater cable lengths, it is not widely used.

RS-423 systems can transmit data on cables as long as 1,200 meters (3,900 ft).^{[dubious – discuss]} It is closely related to RS-422, which used the same signaling systems but on a different wiring arrangement: RS-423 differed primarily in that it had a single return pin instead of one for each data pin.^[1]

RS-423 specifies an unbalanced (single-ended) interface, similar to RS-232, with a single, unidirectional sending driver, and allowing for up to 10 receivers.^[2] It is normally implemented in integrated circuit technology and can also be employed for the interchange of serial binary signals between DTE & DCE.

Standard scope[edit]

RS-423 is the common short form title of American National Standards Institute (ANSI) standard ANSI/TIA/EIA-423-B Electrical Characteristics of Unbalanced Voltage Digital Interface Circuits and its international equivalent ITU-T Recommendation T-REC-V.10,^[3] also known as X.26. These technical standards specify the electrical characteristics of the unbalanced voltage digital interface circuit.^[4] RS-423 provides for data transmission, using unbalanced or single-ended signals, with unidirectional/non-reversible, terminated or non-terminated transmission lines, point to point, or multi-drop.

Characteristics[edit]

RS-423 is closely related to the RS-422 standard, both of which use the same overall signaling system, but differ in that RS-422 has a dedicated return line for every data pin, while RS-423 uses a single return line. Use of a common ground is one weakness of RS-423 (and RS-232): if devices are far enough apart or on separate power systems, the ground will degrade between them and communications will fail, resulting in a condition that is difficult to trace.^[5]

RS-423 specifies the electrical characteristics of a single unbalanced signal. The standard was written to be referenced by other standards that specify the complete DTE/DCE interface for applications which require a unbalanced voltage circuit to transmit data.^{[citation needed]}

These other standards would define protocols, connectors, pin assignments and functions. Standards such as EIA-530 (DB-25 connector) and EIA-449 (DC-37 connector) use RS-423 electrical signals.^{[citation needed]}

Applications[edit]

The BBC Micro computer uses RS-423 with a 5-pin DIN connector. DEC used it extensively with a Modified Modular Jack connector. This was sometimes called "DEC-423".^{[citation needed]}

References[edit]

^ "EIA-423". foldoc.org. Retrieved 2021-07-08.
^ Buchanan W.J. (2004) RS-422, RS-423 and RS-485. In: The Handbook of Data Communications and Networks. Springer, Boston, MA.ISBN 978-1-4757-1067-0 page 627
^ "V.10 : Electrical characteristics for unbalanced double-current interchange circuits operating at data signalling rates nominally up to 100 kbit/s". itu.int. Retrieved 3 May 2023.
^ TIA/EIA STANDARD, Electrical Characteristics of Unbalanced Voltage Digital Interface Circuits, TIA/EIA-423-B, May 1993
^ National Semiconductor Application Note AN-1031 "TIA/EIA-422-B Overview", January 2000, National Semiconductor Inc. page 2 - evaluate the combination of cable length and data rate.

v t e Technical and de facto standards for wired computer buses
General	System bus Front-side bus Back-side bus Daisy chain Control bus Address bus Bus contention Bus mastering Network on a chip Plug and play List of bus bandwidths
Standards	SS-50 bus S-100 bus Multibus Unibus VAXBI MBus STD Bus SMBus Q-Bus Europe Card Bus ISA STEbus Zorro II Zorro III CAMAC FASTBUS LPC HP Precision Bus EISA VME VXI VXS NuBus TURBOchannel MCA SBus VLB HP GSC bus InfiniBand Ethernet UPA PCI PCI Extended (PCI-X) PXI PCI Express (PCIe) AGP Compute Express Link (CXL) Direct Media Interface (DMI) RapidIO Intel QuickPath Interconnect NVLink HyperTransport Infinity Fabric Intel Ultra Path Interconnect Coherent Accelerator Processor Interface (CAPI) SpaceWire
Storage	ST-506 ESDI IPI SMD Parallel ATA (PATA) SSA DSSI HIPPI Serial ATA (SATA) SCSI Parallel SAS Fibre Channel SATAe PCI Express (via AHCI or NVMe logical device interface)
Peripheral	Apple Desktop Bus Atari SIO DCB Commodore bus HP-IL HIL MIDI RS-232 RS-422 RS-423 RS-485 Lightning DMX512-A IEEE-488 (GPIB) IEEE-1284 (parallel port) IEEE-1394 (FireWire) UNI/O 1-Wire I²C (ACCESS.bus, PMBus, SMBus) I3C SPI D²B Parallel SCSI Profibus USB Camera Link External PCIe Thunderbolt
Audio	ADAT Lightpipe AES3 Intel HD Audio I²S MADI McASP S/PDIF TOSLINK
Portable	PC Card ExpressCard
Embedded	Multidrop bus CoreConnect AMBA (AXI) Wishbone SLIMbus
Interfaces are listed by their speed in the (roughly) ascending order, so the interface at the end of each section should be the fastest. Category

RS-423

Standard scope[edit]

Characteristics[edit]

Applications[edit]

See also[edit]

References[edit]

Further reading[edit]