IEbus Electrical Interface
IEBus [Inter Equipment Bus] is used as an In-vehicle [Automotive] support bus using half duplex asynchronous [Multi-Master] communication with CSMA/CD [Carrier Sense Multiple Access/Collision Detection] for access control. Two differential lines are used; Data+ / Data-. Two modes are defined: Mode 0 uses 16 bytes/frame and runs at 3.9kbps or 4.1kbps. Mode 1 uses 32 bytes/frame and runs at 17kbps [6MHz Osc.] or 18kbps [6.29MHz Osc.]. The IEbus allows 50 units on the bus over a maximum length of 50 meters. The IEbus is a 2-wire bus.
The cable capacitance is rated to have 8000pF max [6MHz] or 7100pF max [6.29MHz]. It appears that load capacitors should be added between each data bus line and ground to insure that those capacitance values are meet. CTotal = 1/2 * CLoad + CWire. The bus is terminated to 120 ohms [+/- 5%] at each end. Series protection resistors of 180 ohms [+/- 5%] are also used. With both lines within 20mV or less a logic high is represented, when the Bus lines are different by 120mV or more a Logic 0 is produced. The bus voltage level are -0.5v to +6.0 volts.
For the graph above; the length of time for all the fields in Mode 0 is
7330uS + (1590 x [ number of data fields])uS. In Mode 1 the transmission
time is 2090uS + (410 x [number of data fields])uS. P = Parity bit, A =
Acknowledge bit.
Synchronization is done for every bit transmitted. The bus is idle high,
taken low for the Synchronization period, then the bus enters the data
period. During the data period the bus is either taken high or low
depending on the data bit sent. After the data period the bus returns to
the preparation period, and is idle high. Each device on the bus has a 12
bit address. The IEBus was developed by NEC Electronics.
The main Automotive Buses page.
Electronic Engineering Design Key words: IEbus, Inter Equipment Bus, IEBus protocol, Automotive Buses, Auto Bus types, Motor vehicle Bus Standard, Passenger cars, Interface Standard Data Bus, Specification, Spec, Interface, IC, Physical Interface, Topology, Description, Physical Interface, X-by-wire, Automotive, Auto, Car, Carmaker, Cable Bus, In-vehicle, IEbus Transmission Signal Format, IE-Bus.
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