Claims
- 1. A method of granting bus access to one of first and second modules seeking control of a common bus, the method comprising:assigning a first module priority level to the first module; assigning a second module priority level to the second module; assigning a first arbitration number to the first module; assigning a second arbitration number to the second module; when the first and second module priority levels are not the same, granting bus access to a module with a module priority level having a higher priority; when the first and second module priority levels are the same, granting bus access to the module that has been waiting its turn longer; and when the first and second module priority levels are the same and each of the first and second modules has been waiting its turn, comparing the first and second arbitration numbers and granting access to the module with an arbitration number having a higher arbitration priority.
- 2. The method as recited in claim 1 wherein the first and second arbitration numbers are unique for a given module priority level.
- 3. The method as recited in claim 1, wherein a lowest value module priority level has the higher priority.
- 4. The method as recited in claim 1, wherein a highest value module priority level has the higher priority.
- 5. The method as recited in claim 1, wherein a lowest value arbitration number has the higher arbitration priority.
- 6. The method as recited in claim 1, wherein a highest value arbitration number has the higher arbitration priority.
- 7. The method as recited in claim 1, wherein the first and second modules are connected to an arbitration data bus having two lines on which the first and second arbitration numbers are compared in a round-robin mode of operation.
- 8. The method as recited in claim 7 wherein the arbitration data bus has a WIRED-OR bus configuration.
- 9. The method as in claim 1, wherein granting bus access to the module that has been waiting its turn longer comprises determining whether one of the first and second modules has been previously granted bus access and is asserting a new request and the other has been waiting its turn.
- 10. The method as in claim 1, wherein comparing the first and second arbitration numbers comprises determining whether the first and second modules have been waiting their turns for similar lengths of time.
- 11. A method of bus arbitration for a system comprising first and second modules connected by a bus having a plurality of data lines and an arbitration unit, the method comprising:signaling a first bus request to the bus for the first module needing to transmit a first plurality of data packets on to the bus, the first module having a first module priority level and a first arbitration number; signaling a second bus request to the bus for the second module needing to transmit a second plurality of data packets on to the bus, the second module having a second module priority level and a second arbitration number; setting a bus priority level according to a comparison of the first module priority level and the second module priority level wherein the bus priority level is set to one of the first and second module priority levels as determined by which module priority level has a higher priority than the other; when the first and second module priority levels are not the same, scheduling the transmission of a module with the module priority level equal to the bus priority level first, when the first and second module priority levels are the same: determining whether each of the first and second modules has either been previously granted bus access and is asserting a new request or has been waiting its turn for the bus; and when one module has been previously granted bus access and the other is waiting, scheduling the transmission of the module that has been waiting for the bus first, and when the first and second module priority levels are the same, and each module has been waiting for the bus: asserting the first arbitration number on the bus for the first module; asserting the second arbitration number on the bus for the second module; comparing the first arbitration number and the second arbitration number; and scheduling the transmission of the module with an arbitration number having a higher arbitration priority first.
- 12. The method as recited in claim 11 wherein the first and second arbitration numbers are unique for a given module priority level.
- 13. A method of bus arbitration for a system comprising first and second modules connected by a bus having a plurality of data lines and an arbitration unit, the method comprising:signaling a first bus request to the bus for the first module needing to transmit a first plurality of data packets on to the bus, the first module having a first module priority level and a first arbitration number; signaling a second bus request to the bus for the second module needing to transmit a second plurality of data packets on to the bus, the second module having a second module priority level and a second arbitration number; when the first and second module priority levels are not the same, scheduling transmission of a module with a module priority level having a higher priority; when the first and second module priority levels are the same: determining whether each of the first and second modules has either been previously granted bus access and is asserting a new request or has been waiting its turn for the bus; and when one module has been previously granted bus access the other is waiting its turn for the bus, scheduling the transmission of the module that has been waiting its turn for the bus first, and when the first and second module priority levels are the same, and each module has been waiting for the bus: asserting the first arbitration number on the bus for the first module; asserting the second arbitration number on the bus for the second module; comparing the first arbitration number and the second arbitration number; and scheduling the transmission of the module with an arbitration number having a higher arbitration priority first.
- 14. The method as recited in claim 13, wherein the bus includes an arbitration data bus including two data lines.
- 15. The method as recited in claim 14, wherein the arbitration data bus is set to a wait state in response to one of the following conditions:a reset signal on the arbitration data bus; a deasserting signal from one of the modules; an “exit from arbitration” signal from one of the modules; a “lose arbitration” signal from one of the modules; and a “win arbitration” signal from one of the modules.
- 16. The method as recited in claim 14, wherein the two data lines of the bus include:an ARB13STROBE line, the ARB13STROBE line carrying a WIRED-OR signal asserted by the first and second modules during an arbitration sequence; and an ARB13DATA line, the ARB13DATA line carrying a signal used for an arbitration signaling process.
- 17. The method as recited in claim 13, wherein a lowest value module priority level has the higher priority.
- 18. The method as recited in claim 13, wherein a highest value module priority level has the higher priority.
- 19. The method as recited in claim 13, wherein a lowest value arbitration number has the higher arbitration priority.
- 20. The method as recited in claim 13, wherein a highest value arbitration number has the higher arbitration priority.
- 21. The method as recited in claim 13, wherein the first and second modules are connected to an arbitration data bus having two lines on which the first and second arbitration numbers are compared.
- 22. The method as recited in claim 21, wherein the arbitration data bus has a WIRED-OR bus configuration.
- 23. A method of granting bus access to one of first and second modules seeking control of a common bus, the first module having a first module priority level and a first arbitration number, and the second module having a second module priority level and a second arbitration number, the method comprising:when the first and second module priority levels are not the same, granting bus access to a module with a module priority level having a higher priority; when the first and second module priority levels are the same, granting bus access to the module that has been waiting its turn longer; and when the first and second module priority levels are the same and each of the first and second modules has been waiting its turn, comparing the first and second arbitration numbers and granting access to the module with an arbitration number having a higher arbitration priority.
- 24. The method as recited in claim 23, wherein a lowest value module priority level has the higher priority.
- 25. The method as recited in claim 23, wherein a highest value module priority level has the higher priority.
- 26. The method as recited in claim 23, wherein a lowest value arbitration number has the higher arbitration priority.
- 27. The method as recited in claim 23, wherein a highest value arbitration number has the higher arbitration priority.
- 28. The method as recited in claim 23, wherein the first and second modules are connected to an arbitration data bus having two lines on which the first and second arbitration numbers are compared.
- 29. The method as recited in claim 28, wherein the arbitration data bus has a WIRED-OR bus configuration.
- 30. The method as in claim 23, further comprising:assigning the first module priority level to the first module.
- 31. The method as in claim 23, further comprising:assigning the second module priority level to the second module.
- 32. The method as in claim 23, further comprising:assigning the first arbitration number to the first module.
- 33. The method as in claim 23, further comprising:assigning the second arbitration number to the second module.
- 34. The method as in claim 23, wherein granting bus access to the module that has been waiting its turn longer comprises determining whether one of the first and second modules has been previously granted bus access and is asserting a new request and the other has been waiting its turn.
- 35. The method as in claim 23, wherein comparing the first and second arbitration numbers comprises determining whether the first and second modules have been waiting their turns for similar lengths of time.
- 36. An apparatus for granting bus access to one of first and second modules seeking control of a common bus, the first module having a first module priority level and a first arbitration number assigned to it and the second module having a second module priority level and a second arbitration number assigned to it, the apparatus comprising:a first circuit that grants bus access to a module with a module priority level having a higher priority when the first and second module priority levels are not the same; a second circuit that determines, when the first and second module priority levels are the same, whether one of the first and second modules has been previously granted bus access and is asserting a new request and the other has been waiting its turn and then grants bus access to the module that has been waiting its turn; and a third circuit that compares, when the first and second module priority levels are the same and each of the first and second modules has been waiting its turn, the first and second arbitration numbers and then grants access to the module with an arbitration number having a higher arbitration priority.
- 37. The apparatus as recited in claim 36, wherein the first and second modules are connected to an arbitration data bus having two lines on which the first and second arbitration numbers are compared.
- 38. The apparatus as recited in claim 37, wherein the arbitration data bus has a WIRED-OR bus configuration.
- 39. An apparatus for granting bus access to one of first and second modules seeking control of a common bus, the first module having a first module priority level and a first arbitration number assigned to it and the second module having a second module priority level and a second arbitration number, assigned to it, the apparatus comprising:means for granting bus access to a module with a module priority level having a higher priority when the first and second module priority levels are not the same; means for determining, when the first and second module priority levels are the same, whether one of the first and second modules has been previously granted bus access and is asserting a new request and the other has been waiting its turn and for granting bus access to the module that has been waiting its turn; and means for comparing, when the first and second module priority levels are the same and each of the first and second modules has been waiting its turn, the first and second arbitration numbers and for granting access to the module with an arbitration number having a higher arbitration priority.
- 40. The apparatus as recited in claim 39, wherein the first and second modules are connected to an arbitration data bus having two lines on which the first and second arbitration numbers are compared.
- 41. The apparatus as recited in claim 40, wherein the arbitration data bus has a WIRED-OR bus configuration.
Parent Case Info
This application is a continuation of Ser. No. 08/774,775 filed Dec. 30, 1996 now U.S. Pat. No. 5,898,694.
US Referenced Citations (11)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0159592 |
Oct 1985 |
EP |
2287621 |
Sep 1995 |
GB |
Continuations (1)
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Number |
Date |
Country |
Parent |
08/774775 |
Dec 1996 |
US |
Child |
09/256041 |
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US |