IEBus

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.IEBus is also used in some vending machines, which major customer is Fuji Electric.: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.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 CSMA/CD (Carrier Sense Multiple Access/Collision Detection) for access control.:7 It allows for up to fifty units on one bus over a maximum length of 150 meters.:7 Two differential signalling lines are used with Bus+ / Bus− naming,:5 sometimes labeled as Data(+) / Data(−).P: Parity bit (1 bit); Even parityA: Acknowledge bit (1 bit)    When A = 0: ACK    When A = 1: NAK    In broadcast communication, the value of the acknowledge bit is ignored.N: Number of data bytes 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.IEBus is also used in some vending machines, which major customer is Fuji Electric.: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.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 CSMA/CD (Carrier Sense Multiple Access/Collision Detection) for access control.:7 It allows for up to fifty units on one bus over a maximum length of 150 meters.:7 Two differential signalling lines are used with Bus+ / Bus− naming,: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.2552418and 2552419, respectively). In the middle of '80s, semiconductor unit of NEC Corporation, currently Renesas Electronics, started the study for increasing demands for automotive audio systems.IEBus is introduced as a solution for the distributed control system.:18 In the late 1980s, several similar specifications, including the Domestic Digital Bus (D2B), the Japanese Home Bus (HBS),and the European Home System (EHS) are proposed by different companies or organizations. These were once discussed as IEC 61030,but it was withdrawn in 2006. IEBus is also a similar specification (refer to 'Transfer signal format' section), but not listed in this criteria. As the result, IEBus becomes a de facto standard of car audio in Japan.:353Regarding the Domestic Digital Bus (D2B), it is re-defined as D2B Optical by Mercedes-Benz independently.As for Japanese Home Bus System (HBS), it is defined in 1988 as Home Bus System Standard Specification, ET-2101 by JEITA and REEA (Radio Engineering & Electronics Assiation) in Japan. It was once used by a Japanese air conditioner manufacture. Fujitsu provided HBPC (Home Bus Protocol Coltroller) chip as MB86046B. But it is unclear that Fujitsu (currently, Cypress) still manufactures HBPC LSI as of 2018. This specification is also discussed in Echonet Consortium.In 2014, a utility model patent for protocol converter from HBS to RS-485 is granted in China as 'CN204006496U.' Regarding the replacement of IEBus, a paper by Hyundai Autonet, currently Hyundai Mobis,describes as follows. 'In communication methods for digital input capable amplifiers, Inter Equipment Bus (IEBus) was used in early times, but for now, Controller Area Network (CAN) is mainly used.' A master talks to a slave. Each unit has a master and a slave address register. Only one device can talk on the bus at any given time. There is a pecking order for the types of communications which will take precedence over another. Each communication from master to slave must be replied to by the slave going back to the master with acknowledge bits each of those show ACK or NAK.:10 If the master does not receive the ACK within a predefined time allowance for a mode, it drops the communication and returns to its standby (listen) mode. Detailed specification of OSI model layer 2 is disclosed to licensees only, but protocol analyzers are provided from some test equipment vendors.In 2012, one of Chinese manufacturer's patent is granted as 'CN202841169U'. An open-source software emulator called 'IEBus Studio' exists on a repository of SourceForge, but the last update was on 2008-02-24.Another open-source analyzer software called 'IEBusAnalyzer' is available on GitHub repository.Some hobbyist made some tools also. From µPD6708 data sheet.:7and µPD78098B Subseries user's manual, hardware.:428