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

Patent metadata

Field	Value
Publication number	US-9864724-B2
Application number	US-201214129588-A
Country	US
Kind code	B2
Filing date	Jun 26, 2012
Priority date	Jun 29, 2011
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

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.

First claim

What is claimed is:

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

Assignees

• Hartwich Florian
• Horst Christian
• Bosch Gmbh Robert

Inventors

• Hartwich Florian
• Horst Christian

Classifications

• H04L2001/0094

  Bus · CPC title

• G06F13/4282

  on a serial bus, e.g. I2C bus, SPI bus (on daisy chain buses G06F13/4247) · CPC title

• H04L2012/40215

  Controller Area Network CAN · CPC title

• H04L1/0083

  Formatting with frames or packets; Protocol or part of protocol for error control · CPC title

• G06F13/4291 Primary

  using a clocked protocol · CPC title