IEBus

IEBus (Inter Equipment Bus)

Communication protocol
μPD72042B protocol controller made by NEC
Purpose	Communication between equipments within a vehicle or a chassis. e.g.) Car audio,Vending machine,etc.
Developer(s)	Renesas (formerly NEC Electronics)
Introduction	1993; 31 years ago (1993)
Based on	PWM (pulse-width modulation) Base clock: 6.000 MHz (6.291 MHz)
OSI layer	"Physical" and "Data link" layer
Hardware	IEBus controller & Transceiver

IEBus (Inter Equipment Bus) is a communication bus specification "between equipments within a vehicle or a chassis" of Renesas Electronics. It defines OSI model layer 1 and layer 2 specification. IEBus is mainly used for car audio and car navigations, which established de facto standard in Japan, though SAE J1850 is major in United States.^[1]
IEBus is also used in some vending machines, which major customer is Fuji Electric.^{[2]: 244(42)} Each button on the vending machine has an IEBus ID, i.e. has a controller.
Detailed specification is disclosed to licensees only, but protocol analyzers are provided from some test equipment vendors.^[3] Its modulation method is PWM (Pulse-Width Modulation) with 6.00 MHz base clock originally, but most of automotive customers use 6.291 MHz, and physical layer is a pair of differential signalling harness. Its physical layer adopts half-duplex, asynchronous, and multi-master communication with carrier-sense multiple access with collision detection (CSMA/CD) for medium access control.^[4]: 7 It allows for up to fifty units on one bus over a maximum length of 150 meters.^[4]: 7 Two differential signalling lines are used with Bus+ / Bus− naming,^[4]: 5 sometimes labeled as Data(+) / Data(−).

It is sometimes described as "IE-BUS", "IE-Bus," or "IE Bus," but these are incorrect. In formal, it is "IEBus." IEBus® and Inter Equipment Bus® are registered trademark symbols of Renesas Electronics Corporation, formerly NEC Electronics Corporation, (JPO: Reg. No.2552418^[5] and 2552419,^[6] respectively).