Method and apparatus for adapting the data transmission security in a serial bus system

A method for serial data transmission in a bus system having at least two subscribed data processing units, the method comprising:

• exchanging messages via the bus;
• providing that the transmitted messages have a logical structure according to CAN standard ISO 11898-1, the logical structure including a start-of-frame bit, an arbitration field, a control field, a data field, a CRC field, an acknowledge field and an end-of-frame sequence;
• providing that the control field includes a data length code, which contains information about the length of the data field;
• wherein as a function of the content of the data length code, the CRC field of transmitted messages may have at least two different numbers of bits.

A device for serial data transmission in a bus system having at least two subscribed data processing units, comprising:

• an exchange arrangement to exchange messages via the bus;
• wherein the transmitted messages having a logical structure according to the CAN standard ISO 11898-1, the logical structure including a start-of-frame bit, an arbitration field, a control field, a data field, a CRC field, an acknowledge field and an end-of-frame sequence,
• wherein the control field including a data length code, which contains information about the length of the data field, and
• wherein, as a function of the content of the data length code, the CRC field of the transmitted messages may have at least two different numbers of bits.

A method for serial data transmission in a bus system having at least two subscribed data processing units, for use in normal operation of a motor vehicle for transmitting data between the at least two subscribed data processing units of the motor vehicle, the method comprising:

• exchanging messages via the bus;
• providing that the transmitted messages have a logical structure according to CAN standard ISO 11898-1, the logical structure including a start-of-frame bit, an arbitration field, a control field, a data field, a CRC field, an acknowledge field and an end-of-frame sequence;
• providing that the control field includes a data length code, which contains information about the length of the data field;
• wherein as a function of the content of the data length code, the CRC field of transmitted messages may have at least two different numbers of bits.

A method for serial data transmission in a bus system having at least two units, for use during the manufacturing or maintenance of a motor vehicle for transmitting data between a programming unit connected to the data bus for programming purposes and at least one control unit of the motor vehicle that is connected to the data bus, the method comprising:

• exchanging messages via the bus;
• providing that the transmitted messages have a logical structure according to CAN standard ISO 11898-1, the logical structure including a start-of-frame bit, an arbitration field, a control field, a data field, a CRC field, an acknowledge field and an end-of-frame sequence;
• providing that the control field includes a data length code, which contains information about the length of the data field;
• wherein as a function of the content of the data length code, the CRC field of transmitted messages may have at least two different numbers of bits.