| 摘要 |
In accordance with this invention, an arbitration unit controls access to a shared device between a plurality devices. The arbitration unit grants access to the shared device so that both the maximum latency requirement and the minimum access requirement of the devices are satisfied. In one embodiment, a first device with high access requirements uses the precedence of a second device when the second device has a higher precedence than the first device and the second device does not request access to the shared device. Thus the first device can receive access to the shared device based on the precedence of the second device or the precedence of the first device. In another embodiment, the devices are circularly ordered to determine the precedence of each device. In accordance with circular arbitration, after the first device receives access to the shared device based on the precedence of the second device, the second device is assigned the lowest precedence. Furthermore, some embodiments arrange the devices in a hierarchy of different groups. A first group within a second group is treated as a single device of the second group. One implementation of the arbitration unit includes a group pointer for each group and a precedence decoder.
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