A | B | C | D | E | F | G | H | CH | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
| 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 |
| 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).
History
In the middle of '80s, semiconductor unit of NEC Corporation, currently Renesas Electronics, started the study for increasing demands for automotive audio systems.[7] IEBus is introduced as a solution for the distributed control system.[8]: 18
In the late 1980s, several similar specifications, including the Domestic Digital Bus (D2B), the Japanese Home Bus (HBS),[9][10][11]
and the European Home System (EHS) are proposed by different companies or organizations. These were once discussed as IEC 61030,[12]
but it was withdrawn in 2006. IEBus is also a similar specification (refer to "Transfer signal format" section), but not listed in these criteria. As the result, IEBus becomes a de facto standard of car audio in Japan.[citation needed]
Regarding 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 is being used by several Japanese air conditioner manufacturers (for example, M-Net from Mitsubishi[13] and the P1/P2 or F1/F2 bus from Daikin[14][15]). Fujitsu provided HBPC (Home Bus Protocol Controller) chip as MB86046B.[11] But it is unclear whether Fujitsu (currently, Cypress) still manufactures this HBPC LSI as of 2018. Mitsumi Electric provides the MM1007 and MM1192 driver ICs for HBS. The HBS specification is also discussed in the Echonet Consortium.[16][17][18][19][20]
In 2014, a utility model patent for protocol converter from HBS to RS-485 is granted in China as "CN204006496U."
[21]
Regarding the replacement of IEBus, a paper by Hyundai Autonet, currently Hyundai Mobis,[22] 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."[23]
Protocol overview
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.[4]: 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.[3][24] In 2012, one of Chinese manufacturer's patent is granted as "CN202841169U".[25]
An open-source software emulator called "IEBus Studio" exists on a repository of SourceForge, but the last update was on 2008-02-24.[26][27] Another open-source analyzer software called "IEBusAnalyzer" is available on GitHub repository.[28] Some hobbyist made some tools also.[29]
Physical layer (OSI model layer 1) specification overview
From μPD6708 data sheet.[4]: 7 and μPD78098B Subseries user's manual, hardware.[30]: 428
- Communication system
- Half-duplex asynchronous communication
- Multi-master system
- All the units connected to the IEBus can transfer data to the other units.
- Broadcast communication function (communication between one unit and multiple units)
- Normally, communication is individually carried out from one unit to another. By using the broadcast communication function, however, communication can be executed from one unit to plural units as follows:
- Group broadcast communication: Broadcast communication to group units
- Simultaneous broadcast communication: Broadcast communication to all units
- Effective transmission rate
- The effective transmission rate can be selected from the following three communication modes:
- Mixture of the plural of modes in the same bus line is not allowed.
- Correct communication between different base clock is not possible.
Mode Maximum Number of Transfer Bytes
(bytes/frame)6.000000 MHz
base clock6.291456 MHz
base clock0 16 Approx. 3.9 kbit/s Approx. 4.1 kbit/s 1 32 Approx. 17 kbit/s Approx. 18 kbit/s 2 128 Approx. 26 kbit/s Approx. 27 kbit/s
- Access control
- CSMA/CD (Carrier Sense Multiple Access with Collision Detection)
- The priority of occupying IEBus is as follows:
- «1» Broadcast communication takes precedence over individual communication.
- «2» The lower the master address, the higher the priority.
- Communication scale
- Number of units: 50 MAX.
- Cable length: 150 m MAX. (when a twisted pair cable is used)
- Load capacity:
MAX. 8000 pF; between Bus+ and Bus−, (6.000000 MHz base clock)
MAX. 7100 pF; between Bus+ and Bus−, (6.291456 MHz base clock) - Terminating resistor: 120 Ω
- Logic level[4]: 19, 66
- Logic 1: Low level. Voltage difference between Bus+ and Bus− is under 20mV
- Logic 0: High Level. Voltage difference between Bus+ and Bus− is over 120mV
- In-phase input voltage high: Bus+ ≤ (VDD-1.0) V, Bus− ≥ 1.0 V
Transfer signal format
From μPD6708 data sheet.[4]: 10 and μPD78098B Subseries user's manual, hardware.[30]: 433
This frame format is much similar to that of Domestic Digital Bus (D2B).[31]: §10.2, p.361
- All fields are MSB first.
Field name Header Master
address
fieldSlave
address
fieldControl
fieldMessage
length
fieldData fields Data 1 ··· Data N Number of bits 1 1 12 1 12 1 1 4 1 1 8 1 1 8 1 1 ··· 8 1 1 Signal format Start
bitBroad-
cast
bitMaster
addressP Slave
addressP A Control
bitP A Message
length
bitP A Data
bitP A ··· Data
bitP A Transfer time At 6.000 MHz base clock ← Mode 1 Approx. 7370 μs Approx. 1590×N μs Mode 2 Approx. 2090 μs Approx. 410×N μs Mode 3 Approx. 1590 μs Approx. 300×N μs Remark P: Parity bit (1 bit); Even parity
A: 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