Method of communication with coherence checking and device for the implementation thereof

• US 6,771,716 B1
• Filed: 01/12/1999
• Issued: 08/03/2004
• Est. Priority Date: 01/14/1998
• Status: Expired due to Term

• Current Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Gaultier, Jean-Marie
• Primary Examiner(s): Corrielus, Jean B.
• Application Number:
  US09/229,127
• Time in Patent Office: 2,030 Days
• Field of Search: 375/340, 375/369, 375/259, 375/260, 375/213, 714/709, 714/800, 714/802, 714/819, 714/825
• US Class Current: 375/340
• CPC Class Codes: G06F 13/4291 using a clocked protocol
• CPC Class Codes: H04L 25/45 using electronic distributors

Abstract

A method of communication between a master unit and a slave unit is of the type including the transmission of messages comprising a useful information word, as well as one or more service bits. The messages include two bits to encode the end-of-transmission information. The value of these bits provides information on the nature of the useful information transmitted to thereby improve the integrity of the communications.

Claims

1. A method of communicating between a master unit and a slave unit, comprising:

generating a message, at the master unit, comprising at least one service bit and a useful information word of a specified type, the at least one service bit comprising at least one coherence bit having a value signifying the specified type of the useful information word;

transmitting the message from the master unit to the slave unit;

receiving the message at the slave unit;

extracting the useful information word and the at least one coherence bit from the received message;

decoding a value of the at least one coherence bit;

incrementing a reception counter based upon a check between the specified type of useful information transmitted and the value of the at least one coherence bit; and

directing the useful information word based upon a value of the reception counter.

2. A method according to claim 1, wherein the at least one coherence bit comprises a word of at least two coherence bits.

3. A method according to claim 1, wherein the at least one coherence bit also indicates an end of the message.

4. A method according to claim 1, wherein the useful information word is one of a control instruction, a memory address, and a data element.

5. A method according to claim 1, wherein the at least one coherence bit has a value establishing a distinction between most significant bits and least significant bits of a memory address.

6. A method according to claim 1, wherein the at least one coherence bit has a value establishing a distinction between most significant bits and least significant bits of a transmitted data element.

7. A method according to claim 1, wherein the at least one coherence bit has a different value depending on whether the transmitted message is a read instruction or a write instruction.

8. A method according to claim 1, further comprising the step of transmitting a last useful information word responsive to a transmission that has not been accurately acknowledged.

9. A method according to claim 1, wherein the at least one service bit further comprises at least a start bit.

10. A method according to claim 1, wherein the at least one service bit further comprises at least a check bit.

11. A method of communicating comprising;

generating a message, at a first unit, comprising at least one service bit and a useful information word of a specified type, the at least one service bit comprising at least one coherence bit having a value signifying the specified type of the useful information word;

transmitting the message from the first unit to a second unit;

extracting the useful information word and the at least one coherence bit from the received message at the second unit;

incrementing a reception counter based upon a check between the specified type of useful information transmitted and the at least one coherence bit; and

directing the useful information word based upon a value of the reception counter.

12. A method according to claim 11, wherein the first unit comprises a master unit and the second unit comprises a slave unit.

13. A method according to claim 11, wherein the at least one coherence bit also indicate an end of the message.

14. A method according to claim 11, wherein the useful information word is one of a control instruction, a memory address, and a data element.

15. A method according to claim 11, wherein the at least one coherence bit have a value establishing a distinction between most significant bits and least significant bits of a memory address.

16. A method according to claim 11, wherein the at least one coherence bit have a value establishing a distinction between most significant bits and least significant bits of a transmitted data element.

17. A method according to claim 11, wherein the at least one coherence bit have a different value depending on whether the transmitted message is a read instruction or a write instruction.

18. A method according to claim 11, further comprising the step of transmitting a last useful information word responsive to a transmission that has not been accurately acknowledged.

19. A communication apparatus comprising:

a master unit and a slave unit, said master unit for transmitting messages to said slave unit, each message comprising a useful information word of a specified type and at least one coherence bit having a value signifying the specified type of the useful information word transmitted;

said slave unit comprising

a reception counter,

a reception selector for directing the useful information word in connection with a value of the reception counter, and

a check unit for extracting the useful information word and the at least one coherence bit from a received message, and incrementing the reception counter based upon a check between the specified type of useful information transmitted and the value of the at least one coherence bit.

20. A communication apparatus according to claim 19, wherein the at least one coherence bit comprises a word of at least two coherence bits.

21. A communication apparatus according to claim 19, wherein the at least one coherence bit also indicates an end of the respective message.

22. A communication apparatus according to claim 19, wherein the useful information word is one of a control instruction, a memory address, and a data element.

23. A communication apparatus according to claim 19, wherein the at least one coherence bit has a value establishing a distinction between most significant bits and least significant bits of a memory address.

24. A communication apparatus according to claim 19, wherein the at least one coherence bit has a value establishing a distinction between most significant bits and least significant bits of a transmitted data element.

25. A communication apparatus according to claim 19, wherein the at least one coherence bit has a different value depending on whether the transmitted message is a read instruction or a write instruction.

26. A communication apparatus according to claim 19, wherein said slave unit requests transmission of a last useful information word responsive to a transmission that has not been accurately acknowledged.

27. A method of communicating between a master unit and a slave unit, comprising:

generating a message, at the master unit, comprising at least one service bit and a useful information word of a specified type, the at least one service bit comprising at least one coherence bit having a value signifying the specified type of the useful information word, and the at least one coherence bit also indicating an end of the message; and

transmitting the message from the master unit to the slave unit.

28. A method according to claim 27, wherein the at least one coherence bit comprises a word of at least two coherence bits.

29. A method according to claim 27, wherein the useful information word is one of a control instruction, a memory address, and a data element.

30. A method according to claim 27, wherein the at least one coherence bit has a value establishing a distinction between most significant bits and least significant bits of a memory address.

31. A method according to claim 27, wherein the at least one coherence bit has a value establishing a distinction between most significant bits and least significant bits of a transmitted data element.

32. A method according to claim 27, wherein the at least one coherence bit has a different value depending on whether the transmitted message is a read instruction or a write instruction.

33. A method according to claim 29, wherein the at least one service bit further comprises at least a start bit.

34. A method according to claim 27, wherein the at least one service bit further comprises at least a check bit.