Serial communication device with dynamic allocation of acceptance masks using serial implementation

• US 20040153583A1
• Filed: 09/20/2001
• Published: 08/05/2004
• Est. Priority Date: 09/20/2001
• Status: Abandoned Application

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Microchip Technology Incorporated
• Inventors: Bartling, James E.
• Application Number:
  US09/957,062
• Publication Number:
  US 20040153583A1
• Time in Patent Office: Days
• US Class Current: 710/29
• CPC Class Codes: H04L 12/40032 Details regarding a bus interface enhancer
• CPC Class Codes: H04L 12/4135 using bit-wise arbitration
• CPC Class Codes: H04L 2012/40215 Controller Area Network CAN
• CPC Class Codes: H04L 49/90 Buffering arrangements
• CPC Class Codes: H04L 49/901 using storage descriptor, e.g. read or write pointers

Abstract

A CAN module or a microcontroller comprises a CAN module which receives a serial bit stream. The CAN module comprises a filter register with a bit select input and a single bit output, a bit select unit for selecting a bit of the filter register in accordance with the serial bit stream, a comparator coupled with the single bit output and with the serial bit stream for generating a comparison signal, and a register receiving the comparison signal for accumulating a plurality of comparison results and for generating an acceptance signal.

Claims

1. A CAN module receiving a serial bit stream comprising:

a filter register having a bit select input and a single bit output;

a bit select unit for selecting a bit of said filter register in accordance with said serial bit stream;

a comparator coupled with said single bit output and with said serial bit stream for generating a comparison signal;

a register receiving said comparison signal for accumulating a plurality of comparison results and for generating an acceptance signal.

2. CAN module according to claim 1, further comprising

a mask register having a bit select input and a single bit output;

a mask unit receiving said mask single bit output and said comparison result and generating a result signal being fed to said register.

3. CAN module according to claim 2, further comprising

at least two mask register s having a bit select input and a single bit output;

a multiplexer for selecting one of said mask register single bit output s .

4. CAN module according to claim 3, wherein said multiplexer comprises an input which is coupled with the single bit output of a further filter register.

5. CAN module according to claim 3, wherein said multiplexer comprises an input which is coupled with a constant signal indicating no mask function.

6. CAN module according to claim 3, wherein said multiplexer is controlled by at least one bit from said filter register.

7. CAN module according to claim 6, wherein said filter register comprises two additional bits to control said multiplexer.

8. CAN module according to claim 1, wherein said comparator is an EXCLUSIVE NOR gate.

9. CAN module according to claim 1, wherein said mask unit is a NOR gate.

10. CAN module according to claim 1, wherein said register is a D-Flip-Flop.

11. A microcontroller comprising:

a central processing unit;

a random access memory connected to said central processing unit; and

a CAN module coupled with said central processing unit, wherein said CAN module comprises;

a filter register having a bit select input and a single bit output;

a bit select unit for selecting a bit of said filter register in accordance with said serial bit stream;

a comparator coupled with said single bit output and with said serial bit stream for generating a comparison signal;

a register receiving said comparison signal for accumulating a plurality of comparison results and for generating an acceptance signal.

12. The microcontroller according to claim 11, further comprising:

a mask register having a bit select input and a single bit output;

a mask unit receiving said mask single bit output and said comparison result and generating a result signal being fed to said register.

13. The microcontroller according to claim 12, further comprising:

at least two mask registers having a bit select input and a single bit output;

a multiplexer for selecting one of said mask register single bit outputs.

14. The microcontroller according to claim 13, wherein said multiplexer comprises an input which is coupled with the single bit output of a further filter register.

15. The microcontroller according to claim 13, wherein said multiplexer comprises an input which is coupled with a constant signal indicating no mask function.

16. The microcontroller according to claim 13, wherein said multiplexer is controlled by at least one bit from said filter register.

17. The microcontroller according to claim 16, wherein said filter register comprises two additional bits to control said multiplexer.

18. The microcontroller according to claim 11, wherein said comparator is an EXCLUSIVE NOR gate.

19. The microcontroller according to claim 11, wherein said mask unit is a NOR gate.

20. The microcontroller according to claim 11, wherein said register is a D-Flip-Flop.

21. A method of operating a CAN module comprising the steps of:

receiving a data stream;

generating an identifier and data out of said data stream;

comparing said identifier with a filter value on a bit by bit base;

generating an acceptance signal if said comparison is positive;

storing associated data in a buffer upon generation of said acceptance signal.

22. A method according to claim 21, further comprising the step of masking said comparison result on a bit by bit base.

23. A method according to claim 22, further comprising the step selecting a mask value from a plurality of mask values.

24. A method according to claim 23, wherein said filter value provides additional data information for selecting said mask value.

25. A method according to claim 23, wherein said mask values is selected from a plurality of mask registers and filter registers.

26. A method according to claim 23, wherein one mask value provides a non-masking function.