The SMARTRA unit includes a built-in inductive antenna and electronic circuits connected to the ignition switch. The SMARTRA unit is connected to the engine control unit by a special communication line.
This method of controlling the SMARTRA unit is the most appropriate, since the engine control unit controls the engine start.
How the system works
The immobilizer system includes an engine control unit, a SMARTRA unit and a transponder built into the ignition key.
The engine control unit recognizes the ignition key using a special coding algorithm that operates in parallel in the transponder and the engine control unit. Starting the engine is possible only if the results of the algorithm operation coincide. The memory of the engine control unit stores the data of all transponders attached to the vehicle.
The engine control unit and the SMARTRA unit communicate with each other via a special communication line. During the operation of this connection between the engine control unit and SMARTRA, the line «TO» the engine control unit cannot be used for other types of communication, the engine control unit establishes communication via the line «TO» either with the SMARTRA unit or with other devices (e.g. with a maintenance tester) by turning on the multiplexer and starting special communication procedures. The multiplexer is part of the engine control unit hardware. The SMARTRA communicates via a transponder built into the ignition key. Communication is established at a radio frequency of 125 kHz. The SMARTRA unit is located on the ignition switch next to the frame transceiver radio antenna. The RF signal received by the loop antenna is converted by the SMARTRA unit into messages for serial communication, and the messages from the engine control unit are converted into an RF signal transmitted via the antenna to the transponder.
The SMARTRA unit does not perform transponder identification or coding algorithm calculation. It is an advanced interface that converts the received radio frequency data stream from the transponder into a sequence of messages issued to the engine control unit, and vice versa.
The transponder is of the Hitag 2 type with an improved coding algorithm. When programming the key, special vehicle data is entered into the transponder, which is recorded by it
storage device. The recording procedure is one-time, so the contents of the transponder memory cannot be changed. The data is entered as a 9-byte string compiled at the factory. The contents of the transponder memory are divided into two chains, which are named «identifier» And «key password».
After this programming, the transponder's memory is locked and its contents cannot be read or changed. The transponder transitions from the state «clean» into a state «programmed».
In addition, each transponder has its own 32-bit IDE identification number. Transponder IDE numbers are unique (do not repeat). The IDE number is entered at the factory and can only be read.
The key identity and password are not transmitted from the engine control unit to the transponder or vice versa. Only the results of the encoding algorithm operation are transmitted. It is almost impossible to calculate special vehicle data from the encoding result.
For key coding or other purposes, the engine control unit is connected to a test device, which can be a factory tester used at Hyundai service stations. Communication is carried out according to the line protocol «TO» engine control unit.