Arbitration unit for prioritizing requests based on multiple request groups

1. An arbitration unit comprising:

an input unit configured to receive a plurality of input requests on a plurality of inputs;

a selection unit coupled to said input unit and configured to prioritize said plurality of inputs into a priority order and during a current arbitration cycle to select up to two of said plurality of input requests having a higher priority than others of said plurality of input requests; and

an output unit coupled to said selection unit and configured to provide an output indicative of which of said up to two of said plurality of input requests were selected;

wherein upon a subsequent arbitration cycle, said selection unit is further configured to reprioritize said plurality of inputs depending upon which of said up to two of said plurality of input requests were selected.

2. The arbitration unit as recited in claim 1 , wherein said selection unit is further configured to reprioritize said plurality of inputs such that during said subsequent arbitration cycle said inputs corresponding to said selected input requests and any other of said plurality of inputs having a higher priority than said selected input requests have a lower priority than all others of said plurality of inputs while maintaining a relative priority order.

3. The arbitration unit as recited in claim 2 , wherein one input request of said up to two of said plurality of input requests has a high priority and another of said up to two of said plurality of input requests has a low priority.

4. The arbitration unit as recited in claim 3 , wherein said selection unit includes a state pointer configured to hold a value corresponding to one of said plurality of inputs having a higher priority than all others of said plurality of inputs.

5. The arbitration unit as recited in claim 4 , wherein said selection unit further includes a control unit coupled to said priority pointer and is configured to store said value within said state pointer.

6. The arbitration unit as recited in claim 5 , wherein said selection unit is configured to select said up to two of said plurality of input requests dependent upon a first and a second selection control signal.

7. The arbitration unit as recited in claim 6 , wherein said control unit is further configured to calculate said value by adding one to a number corresponding to said low priority input request in response to said selection unit selecting two of said plurality of input requests.

8. The arbitration unit as recited in claim 6 , wherein said control unit is further configured to calculate said value by adding one to a number corresponding to said high priority input request in response to said selection unit selecting one of said plurality of input requests.

9. The arbitration unit as recited in claim 6 , wherein in response to selecting none of said plurality of input requests, said selection unit is configured to not reprioritize said plurality of inputs.

10. A method of arbitrating a plurality of input requests received on a plurality of groups of inputs, said method comprising:

prioritizing each of said plurality of groups of inputs into a first priority order;

selecting up to two of said plurality of input requests within each group having a higher priority than others of said plurality of input requests based upon said first priority order;

receiving an indication indicative of said plurality of input requests within a group and prioritizing said indications into a second priority order;

selecting one of said plurality of groups of inputs based upon said second priority order and providing a grant indication indicative of which of said plurality of groups of inputs was selected; and

providing an output indicative of which of said plurality of input requests was selected in response to receiving said grant indication.

11. The method as recited in claim 10 further comprising reprioritizing said plurality of inputs such that during a subsequent arbitration cycle said inputs corresponding to said selected input requests and any other of said plurality of inputs having a higher priority than said selected input requests have a lower priority than all others of said plurality of inputs while maintaining a relative priority order.

12. An arbitration unit for arbitrating a plurality of input requests received on a plurality of groups of inputs, said arbitration unit comprising:

means for prioritizing each of said plurality of groups of inputs into a first priority order;

means for selecting up to two of said plurality of input requests within each group having a higher priority than others of said plurality of input requests based upon said first priority order;

means for receiving an indication indicative of said plurality of input requests within a group and ordering said indications into a second priority order;

means for selecting one of said plurality of groups of inputs based upon said second priority order and providing a grant indication indicative of which of said plurality of groups of inputs was selected; and

means for providing an output indicative of which of said plurality of input requests was selected in response to receiving said grant indication.

13. An arbitration unit comprising:

an input unit configured to receive a plurality of input requests on a plurality of inputs;

a selection unit coupled to said input unit and configured to prioritize said plurality of inputs into a priority order and during a current arbitration cycle to select two or more of said plurality of input requests having a higher priority than others of said plurality of input requests; and

an output unit coupled to said selection unit and configured to provide an output indicative of which of said two or more of said plurality of input requests were selected;

wherein upon a subsequent arbitration cycle, said selection unit is further configured to reprioritize said plurality of inputs depending upon which of said two or more plurality of input requests were selected.

14. The arbitration unit as recited in claim 13 , wherein said selection unit is further configured to reprioritize said plurality of inputs such that during said subsequent arbitration cycle said inputs corresponding to said selected input requests and any other of said plurality of inputs having a higher priority than said selected input requests have a lower priority than all others of said plurality of inputs while maintaining a relative priority order.

15. An arbitration unit comprising:

an input unit configured to receive a plurality of input requests on a plurality of inputs;

a selection unit coupled to said input unit and configured to prioritize said plurality of inputs into a priority order and during a current arbitration cycle, in response to particular combinations of inputs, to select at least two of said plurality of input requests having a higher priority than others of said plurality of input requests; and

an output unit coupled to said selection unit and configured to provide an output indicative of which of said at least two of said plurality of input requests were selected;

wherein upon a subsequent arbitration cycle, said selection unit is further configured to reprioritize said plurality of inputs depending upon which of said at least two of said plurality of input requests were selected.

16. The arbitration unit as recited in claim 15 , wherein said selection unit is configured to select said at least two of said plurality of input requests in response to said particular combinations of inputs including said plurality of input requests being received on at least two of said plurality of inputs.

17. The arbitration unit as recited in claim 15 , wherein said selection unit is configured to select less than two of said plurality of input requests in response to said particular combinations of inputs including said plurality of input requests being received on less than two of said plurality of inputs.

18. The arbitration unit as recited in claim 17 , wherein said selection unit includes a state pointer configured to hold a value corresponding to one of said plurality of inputs having a higher priority than all others of said plurality of inputs.

19. The arbitration unit as recited in claim 18 , wherein said selection unit further includes a control unit coupled to said priority pointer and is configured to store said value within said state pointer.

20. The arbitration unit as recited in claim 19 , wherein said selection unit is configured to select said at least two of said plurality of input requests dependent upon a first and a second selection control signal.

21. The arbitration unit as recited in claim 18 , wherein said control unit is further configured to calculate said value by adding one to a number corresponding to said low priority input request in response to said selection unit selecting two of said plurality of input requests.

22. The arbitration unit as recited in claim 18 , wherein said control unit is further configured to calculate said value by adding one to a number corresponding to said high priority input request in response to said selection unit selecting one of said plurality of input requests.

23. The arbitration unit as recited in claim 18 , wherein in response to selecting none of said plurality of input requests, said selection unit is configured to not reprioritize said plurality of inputs.

24. The arbitration unit as recited in claim 15 , wherein said selection unit is further configured to reprioritize said plurality of inputs such that during said subsequent arbitration cycle said inputs corresponding to said selected input requests and any other of said plurality of inputs having a higher priority than said selected input requests have a lower priority than all others of said plurality of inputs while maintaining a relative priority order.

25. The arbitration unit as recited in claim 15 , wherein one input request of said at least two of said plurality of input requests has a high priority and another of said at least two of said plurality of input requests has a low priority.