Method and apparatus for assigning bus grant requests
Access to a bus is granted to one of a number of requesting communication circuits that each submitted a bus control request during a request period of an arbitration period in response to the entries in a priority table. If a requesting communication circuit has an identity and priority that match the identity and priority of a communication circuit stored in a row of the priority table that corresponds with the arbitration period, access to the bus is granted to the requesting communication circuit.
1. A method of assigning bus grants, the method comprising:
determining if one or more bus grant requests were received during a bus request period, each bus grant request including a number of device characteristics, each bus request period having a corresponding number of stored characteristics; and
outputting a bus grant to a device that output a bus grant request during the bus request period when each device characteristic of the bus grant request matches a corresponding stored characteristic.
2. The method of claim 1 wherein the number of device characteristics include a device identity.
3. The method of claim 2 wherein the number of device characteristics include a device priority.
4. The method of claim 1 and further comprising determining a bus grant recipient when each device characteristic of each bus grant request received during the bus request period fails to match a corresponding stored characteristic.
5. The method of claim 4 and further comprising assigning bus grant requests received during the bus request period to two or more groups based on a device characteristic.
6. The method of claim 5 wherein the device characteristic is a device priority.
7. The method of claim 5 wherein bus grant requests are assigned to a group only when enabled.
8. The method of claim 7 and further comprising:
determining if a first group of the two or more groups has any members;
outputting the bus grant to a device in the first group when the first group has a member;
determining if a second group of the two or more groups has any members when the first group has no members; and
outputting the bus grant to a device in the second group when the second group has a member.
9. The method of claim 5 and further comprising:
determining if a first group of the two or more groups has any members;
outputting the bus grant to a device in the first group when the first group has a member;
determining if a second group of the two or more groups has any members when the first group has no members; and
outputting the bus grant to a device in the second group when the second group has a member.
10. The method of claim 1 and further comprising:
determining if the corresponding number of stored characteristics associated with the bus request period is valid; and
outputting the bus grant to the device only when the corresponding number of stored characteristics associated with the bus request period is valid.
11. A communication device comprising:
a memory to hold a number of stored characteristics for each of a plurality of bus request periods; and
a logic device connected to the memory, the logic device to determine if one or more bus grant requests were received during a bus request period, identify a number of device characteristics associated with each bus grant request received during the bus request period, and output a bus grant to a device that output a bus grant request during the bus request period when each device characteristic of the bus grant request matches a corresponding stored characteristic of the bus request period.
12. The communication device of claim 11 wherein the number of device characteristics include a device identity.
13. The communication device of claim 12 wherein the number of device characteristics include a device priority.
14. The communication device of claim 11 wherein the logic device determines a bus grant recipient when each device characteristic of each bus grant request received during the bus request period fails to match a corresponding stored characteristic.
15. The communication device of claim 14 wherein the logic device assigns bus grant requests received during the bus request period to two or more groups based on a device characteristic.
16. The communication device of claim 15 wherein the device characteristic is a device priority.
17. The communication device of claim 16 wherein bus grant requests are assigned to a group only when enabled.
18. The communication device of claim 17 wherein the logic device:
determines if a first group of the two or more groups has any members;
outputs the bus grant to a device in the first group when the first group has a member;
determines if a second group of the two or more groups has any members when the first group has no members; and
outputs the bus grant to a device in the second group when the second group has a member.
19. The communication device of claim 16 wherein the logic device:
determines if a first group of the two or more groups has any members;
outputs the bus grant to a device in the first group when the first group has a member;
determines if a second group of the two or more groups has any members when the first group has no members; and
outputs the bus grant to a device in the second group when the second group has a member.
20. The communication device of claim 11 wherein the logic device:
determines if the corresponding number of stored characteristics associated with the bus request period is valid; and
outputs the bus grant to the device only when the corresponding number of stored characteristics associated with the bus request period is valid.