Method and device for serial data transmission having a flexible message size and a variable bit length

• US 9,864,724 B2
• Filed: 06/26/2012
• Issued: 01/09/2018
• Est. Priority Date: 06/29/2011
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Hartwich, Florian, Horst, Christian
• Primary Examiner(s): Abad, Farley
• Assistant Examiner(s): Yu, Henry
• Application Number:
  US14/129,588
• Publication Number:
  US 20140244871A1
• Time in Patent Office: 2,023 Days
• Field of Search: 710260, 710313, 370462, 370473, 370475, 340 31
• CPC Class Codes: G06F 13/4282 on a serial bus, e.g. I2C bus, SPI bus on daisy chain buses G06F13/4247
• CPC Class Codes: G06F 13/4291 using a clocked protocol
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04L 12/40169 Flexible bus arrangements arrangements for maintenance or administration involving management of faults; events, alarms H04L41/06; automatic restoration of network faults H04L41/0654
• CPC Class Codes: H04L 2001/0094 Bus
• CPC Class Codes: H04L 2012/40215 Controller Area Network CAN
• CPC Class Codes: H04L 47/36 by determining packet size, e.g. maximum transfer unit [MTU]

Abstract

A method for serial data transfer in a bus system having at least two bus subscribers that exchange messages via the bus, the transmitted messages having a CAN standard ISO 11898-1 structure, where for a first marker (EDL), the control field of the messages, divergently from ISO 11898-1, encompasses more than 6 bits, and for the EDL, the data field of the messages, divergently from ISO 11898-1, may encompass more than 8 bytes, the values of the 4 bits of the data length code being interpreted divergently from ISO 11898-1 to establish the data field size, and for a second marker (BRS), the bit length for at least one predefined or predefinable region within the message assumes a value that is shortened as to the bit length used before the second marker was present, the region beginning at the earliest with the second marker and ending at the latest with the CRC delimiter, and the BRS occurring only when the EDL is present, and occurring in the control field of the messages which encompasses more than 6 bits.

Claims

1. A method for serial data transfer in a bus system having at least two bus subscribers that exchange messages via the bus, the method comprising:

exchanging messages between the at least two bus subscribers via the bus, transmitted ones of the messages having a logical structure in accordance with the CAN standard ISO 11898-1;

providing that when a first marker (EDL) is present in one of the transmitted messages, the control field of the one of the transmitted messages, divergently from the CAN standard ISO 11898-1, encompasses more than six bits, and when the first marker (EDL) is present in the one of the transmitted messages, providing that the data field of the one of the messages, divergently from the CAN standard ISO 11898-1, can encompass more than eight bytes, the values of the four bits of the data length code being interpreted at least in part divergently from the CAN standard ISO 11898-1 to establish the size of the data field; and

providing, when a second marker (BRS) is present in the one of the transmitted messages, that the bit length for at least one predefined or predefinable region within the one of the transmitted messages assumes a value that is shortened with respect to the bit length used before the second marker was present, the region beginning at the earliest with the second marker and ending at the latest with the CRC delimiter, the second marker (BRS) occurring only when the first marker (EDL) is present, and occurring in the control field of the one of the transmitted messages which, divergently from the CAN standard ISO 11898-1, encompasses more than six bits.

2. The method of claim 1, wherein the first marker (EDL) is implemented by a recessive bit in the control field.

3. The method of claim 2, wherein when the first marker is present, the recessive bit of the first marker (EDL) is followed, in all data messages, by at least one dominant bit.

4. The method of claim 1, wherein the second marker (BRS) is implemented by way of a recessive bit in the control field which is transferred later in time than the bit of the first marker (EDL).

5. The method of claim 4, wherein when the second marker is present, the recessive bit of the second marker (BRS) is separated from the recessive bit of the first marker (EDL) by at least one dominant bit.

6. The method of claim 3, wherein when the first marker is present, the edge between the recessive bit of the first marker (EDL) and the at least one subsequent dominant bit is used for resynchronization or hard synchronization of the bit timing of the bus subscribers.

7. The method of claim 1, wherein optionally, as a function of a value of the first switchover condition, each of the possible value combinations of the four bits of the data length code is associated with one of the permissible sizes of the data field.

8. The method of claim 1, wherein the first marker (EDL) is evaluated in the bus subscribers and, as a function of the first marker, the receiving process is adapted to the size of the data field.

9. The method of claim 1, wherein the second marker (BRS) is evaluated in the bus subscribers when the first marker is present, and as a function of the value of the second marker, the receiving process is adapted to the different values of the bit length within a message.

10. The method of claim 1, wherein the at least two different values of the time-related bit length within a message are realized by using at least two different scaling factors to adjust the bus time unit during operation relative to a shortest time unit or to the oscillator clock.

11. The method of claim 1, wherein when a further marker is present, the CRC field of the messages has a number of bits divergent from the CAN standard ISO 11898-1, and/or at least one generator polynomial divergent from the CAN standard ISO 11898-1 is used, where the further marker can match the first marker (EDL).

12. The method of claim 11, wherein the value of the further marker is ascertained in the bus subscribers, and the receiving process is adapted to the size of the CRC field depending on the value of the further marker and/or on the content of the data length code.

13. The method of claim 11, wherein at the beginning of a message, the calculation of at least two CRC checksums using different generator polynomials is started concurrently, and as a function of the value of the further marker, a decision is made as to which result from one of the concurrently started CRC calculations is used.

14. An apparatus for serial data transfer in a bus system having at least two bus subscribers that exchange messages via the bus, comprising:

an exchange arrangement to exchange messages between the at least two bus subscribers via the bus, transmitted ones of the messages having a logical structure in accordance with the CAN standard ISO 11898-1;

a control arrangement to provide that when a first marker (EDL) is present in one of the transmitted messages, the control field of the one of the transmitted messages, divergently from the CAN standard ISO 11898-1, encompasses more than six bits, and when the first marker (EDL) is present in the one of the transmitted messages, providing that the data field of the one of the messages, divergently from the CAN standard ISO 11898-1, can encompass more than eight bytes, the values of the four bits of the data length code being interpreted at least in part divergently from the CAN standard ISO 11898-1 to establish the size of the data field, and to provide, when a second marker (BRS) is present in the one of the transmitted messages, that the bit length for at least one predefined or predefinable region within the one of the transmitted messages assumes a value that is shortened with respect to the bit length used before the second marker was present, the region beginning at the earliest with the second marker and ending at the latest with the CRC delimiter, the second marker (BRS) occurring only when the first marker (EDL) is present, and occurring in the control field of the one of the transmitted messages which, divergently from the CAN standard ISO 11898-1, encompasses more than six bits.

15. The apparatus of claim 14, wherein the first marker (EDL) is implemented by a recessive bit in the control field.

16. A method for serial data transfer, during normal operation of a motor vehicle in order to transfer data between at least two control units of the motor vehicle that are connected via a data bus in a bus system having at least two bus subscribers that exchange messages via the bus, the method comprising:

exchanging messages between the at least two bus subscribers via the bus, transmitted ones of the messages having a logical structure in accordance with the CAN standard ISO 11898-1;

providing that when a first marker (EDL) is present in one of the transmitted messages, the control field of the one of the transmitted messages, divergently from the CAN standard ISO 11898-1, encompasses more than six bits, and when the first marker (EDL) is present in the one of the transmitted messages, providing that the data field of the one of the transmitted messages, divergently from the CAN standard ISO 11898-1, can encompass more than eight bytes, the values of the four bits of the data length code being interpreted at least in part divergently from the CAN standard ISO 11898-1 to establish the size of the data field; and

providing, when a second marker (BRS) is present in the one of the transmitted messages, that the bit length for at least one predefined or predefinable region within the one of the transmitted messages assumes a value that is shortened with respect to the bit length used before the second marker was present, the region beginning at the earliest with the second marker and ending at the latest with the CRC delimiter, the second marker (BRS) occurring only when the first marker (EDL) is present, and occurring in the control field of the one of the transmitted messages which, divergently from the CAN standard ISO 11898-1, encompasses more than six bits.

17. A method for serial data transfer, during production or maintenance of a motor vehicle in order to transfer data between a programming unit connected to a suitable data bus for programming purposes and at least one control unit of the motor vehicle which is connected to the data bus in a bus system having at least two bus subscribers that exchange messages via the bus, the method comprising:

exchanging messages between the at least two bus subscribers via the bus, transmitted ones of the messages having a logical structure in accordance with the CAN standard ISO 11898-1;

providing that when a first marker (EDL) is present in one of the transmitted messages, the control field of the one of the transmitted messages, divergently from the CAN standard ISO 11898-1, encompasses more than six bits, and when the first marker (EDL) is present, providing that the data field of the one of the transmitted messages, divergently from the CAN standard ISO 11898-1, can encompass more than eight bytes, the values of the four bits of the data length code being interpreted at least in part divergently from the CAN standard ISO 11898-1 to establish the size of the data field; and

providing, when a second marker (BRS) is present in the one of the transmitted messages, that the bit length for at least one predefined or predefinable region within the one of the transmitted messages assumes a value that is shortened with respect to the bit length used before the second marker was present, the region beginning at the earliest with the second marker and ending at the latest with the CRC delimiter, the second marker (BRS) occurring only when the first marker (EDL) is present, and occurring in the control field of the one of the transmitted messages which, divergently from the CAN standard ISO 11898-1, encompasses more than six bits.