Bus arbitration using monitored windows of time
View Patent ↗A method for use with a computer system includes permitting a first bus agent to access a bus during predetermined windows of time and preventing a second bus agent from accessing the bus outside of the windows. The first bus agent has a higher priority than the second bus agent. The method includes monitoring the use of the bus by the first bus agent during the window and the regulation durations of the windows are selectively regulated based on the use.
1. A method comprising:
establishing windows of time for a first bus agent to request access to a bus;
for times outside of the windows, denying all requests from the first bus agent to access the bus;
monitoring accesses to the bus during the windows; and
selectively regulating durations of the windows in response to the monitoring.
2. The method of claim 1 , wherein the first bus agent comprises:
a system controller.
3. The method of claim 1 , further comprising:
for times outside of the windows, selectively granting requests from a processor.
4. The method of claim 1 , wherein the act of monitoring comprises:
determining a number of clock cycles in which first bus agent accesses the bus during the window.
5. The method of claim 1 , wherein the act of regulating comprises:
decreasing the duration of one of the windows if the amount of use by the first bus agent approximately increases above a threshold.
6. The method of claim 1 , wherein the act of monitoring comprises:
counting clock cycles when the first bus agent requests ownership of the bus.
7. The method of claim 1 , wherein the bus comprises:
a local bus.
8. A bridge usable with a first bus agent that has higher priority for accesses to a bus than a second bus agent, the bridge comprising:
a circuit adapted to:
permit the first bus agent to access the bus during windows of time and prevent the first bus agent from accessing the bus outside of the windows to permit the second bus agent to access the bus,
monitor use of the bus by the first bus agent during the windows, and
selectively regulate the durations of the windows in response to the monitored use.
9. The bridge of claim 8 , wherein the first bus agent comprises a system controller and the second bus agent comprises a processor.
10. The bridge of claim 8 , wherein the circuit comprises:
a timer adapted to determine a number of clock cycles in which the first bus agent accesses the bus during one of the windows.
11. The bridge of claim 8 , wherein the circuit is adapted to regulate the durations by decreasing the duration of one of the windows if the amount of use of the bus by the first bus agent approximately increases above a threshold.
12. The bridge of claim 8 , wherein the circuit comprises:
a timer adapted to not count clock cycles when the second bus agent accesses the bus and count clock cycles when the first bus agent accesses the bus.