SERIAL DATA COMMUNICATION - CAN MEMORY ERROR DETECTION METHODS

• US 20100299585A1
• Filed: 08/02/2010
• Published: 11/25/2010
• Est. Priority Date: 07/29/2005
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: FOREST, THOMAS M., THOMAS, JAMES K., KATRAK, KERFEGAR K.
• Granted Patent: US 7,904,796 B2
• Time in Patent Office: Days
• US Class Current: 714/807
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 2001/0094 Bus

Abstract

A method is provided for formatting a message, with a first plurality of bits forming a data component, and a second plurality of bits forming a reserved component, for transmission in a vehicle. The method comprises the steps of calculating an initial checksum from the data component, calculating a revised checksum at least from the initial checksum, and storing the revised checksum in the reserved component. The number of bits in the reserved component is less than the number of bits in the data component.

Claims

1. A method of formatting a message for transmission in a vehicle, the message comprising a first plurality of bits forming a data component, a second plurality of bits forming a reserved component, and a third plurality of bits forming an identifier component, the method further comprising the steps of:

calculating an initial checksum from the data component using a processor;

generating at least one integer value representative of the identifier component;

calculating a revised checksum using the initial checksum and the at least one integer value; and

storing the revised checksum in the reserved component, wherein the number of bits in the reserved component is less than the number of bits in the data component.

2. The method of claim 1, wherein the at least one integer value is generated via the processor so that an increase in a value of the identifier component results in an increase in a value of the at least one integer value.

3. The method of claim 2, wherein the at least one integer value is generated via the processor by dividing an initial value of the identifier component by a specified divider, so that when this division occurs the integer value will always be a distinct and unique integer value.

4. The method of claim 1, wherein the initial checksum is calculated via the processor as a bytewise sum of the first plurality of bits forming the data component.

5. The method of claim 1, wherein the revised checksum is inversely related to the initial checksum.

6. The method of claim 5, wherein the step of calculating the revised checksum comprises:

subtracting the initial checksum from a specified value, thereby calculating the revised checksum via the processor.

7. The method of claim 1, wherein the step of calculating the revised checksum comprises:

adding together the at least one integer value and the initial checksum, thereby calculating an intermediate checksum via the processor; and

subtracting the intermediate checksum from a specified value, thereby calculating the revised checksum via the processor.

8. The method of claim 1, wherein:

the initial checksum includes a specific number of bits; and

the specified value is a maximum checksum number for the specific number of bits, minus one.

9. The method of claim 1, wherein a ratio of the number of bits in the reserved component to the number of bits in the data component is less than or equal to 1:

2.

10. The method of claim 9, wherein the ratio of the number of bits in the reserved component to the number of bits in the data component is less than or equal to 1:

4.

11. A method of formatting a message for transmission in a vehicle, the message comprising a plurality of data bytes, each data byte comprising a plurality of data bits and a reserved bit, the reserved bit adjacent to a preceding data bit, and a reserved data byte, the method comprising the steps of:

calculating an inverted value of the preceding data bit of each data byte using a processor;

storing the inverted value of the preceding data bit of each data byte in the reserved bit of such data byte;

calculating a checksum from the plurality of data bytes; and

storing the checksum in the reserved data byte of the message.

12. The method of claim 11, wherein the checksum is an exclusive or checksum calculated from the plurality of data bytes.

13. A method for communications of a vehicle, the method comprising the steps of:

formatting a message for transmission in the vehicle, the message comprising a first plurality of bits forming a data component, a second plurality of bits forming a reserved component, and a third plurality of bits forming an identifier component, as follows;

calculating an initial checksum from the data component using a processor;

generating at least one integer value representative of the identifier component;

calculating a revised checksum using the initial checksum and the at least one integer value; and

storing the revised checksum in the reserved component, wherein the number of bits in the reserved component is less than the number of bits in the data component;

decoding the message, generating decoded data; and

generating a security assessment using the decoded data.

14. The method of claim 13, further comprising the step of:

receiving the message, wherein the step of decoding the message occurs after the message is received.

15. The method of claim 14, wherein:

the step of receiving the message comprises the step of receiving the data component and the revised checksum;

the step of decoding the message comprises the steps of;

copying the received data component of the message, generating a copied data component;

calculating a post-receiving checksum using the copied data component; and

comparing the revised checksum and the post-receiving checksum, generating a comparison; and

the step of generating the security assessment comprises the step of generating the security assessment based on the comparison.

16. The method of claim 13, wherein the at least one integer value is generated via the processor so that an increase in a value of the identifier component results in an increase in a value of the at least one integer value.

17. The method of claim 16, wherein the at least one integer value is generated via the processor by dividing an initial value of the identifier component by a specified divider, so that when this division occurs the integer value will always be a distinct and unique integer value.

18. The method of claim 13, wherein the revised checksum is inversely related to the initial checksum.

19. The method of claim 13, wherein the step of calculating the revised checksum comprises:

adding together the at least one integer value and the initial checksum, thereby calculating an intermediate checksum via the processor; and

subtracting the intermediate checksum from a specified value, thereby calculating the revised checksum via the processor.

20. The method of claim 13, wherein:

the initial checksum includes a specific number of bits; and

the specified value is a maximum checksum number for the specific number of bits, minus one.