IEBus (Inter Equipment Bus) is a two wire bus used in the automotive industry as a communications bus between various devices (usually multimedia devices) by using half duplex asynchronous (multi-master) communication with CSMA/CD (Carrier Sense Multiple Access/Collision Detection) for access control. It allows for up to fifty units on the bus over a maximum length of 50 meters. Two differential lines are used; Data+ / Data-, often labeled as Bus(+) Bus(-).

NOTE: IEBus and Inter Equipment Bus are NEC Electronics Corporation trademarks.

IEBus Protocol

When I get more time I will be writing up a brief description of the step by step communications process. The short version is like this... 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. The IEBus in my Acura appears to run at about 50 MHz. Each communication from master to slave must be replied to by the slave going back to the master with an ACK (ackowledge) bit. If the master does not receive the ACK within a predetermined time allowance it drops the communication and returns to its standby (listen) mode.

Mode 0 Uses 16 bytes/frame and runs at 3.9 kbit/s or 4.1 kbit/s. Mode 1 Uses 32 bytes/frame and runs at 17 kbit/s [6 MHz Osc.] or 18 kbit/s [6.29 MHz Osc.]

Automotive Manufacturers Using IEBus

Honda/Acura GA-NET II Toyota AVC-LAN Pioneer IP-Bus