Patent ID: 7251702

Claim:
A network controller having transmitting and receiving buffers, comprising an internal arbiter monitoring the transmitting and receiving buffers, and arbitrating access to a system bus between the transmitting and receiving buffers in response to requests for access to the system bus from the transmitting and receiving buffers, wherein the internal arbiter comprises: an emergency mode determination circuit receiving an occupancy level of data in the receiving buffer and a vacancy level of data in the transmitting buffer, determining whether a present operational state corresponds to an emergency mode as a function of the occupancy level and the vacancy level, and outputting an emergency mode signal on an emergency mode signal line, wherein the emergency mode determination circuit comprises: a first comparing circuit comparing the occupancy level of the receiving buffer with a threshold occupancy level of the receiving buffer and outputting a first comparison result signal; a second comparing circuit comparing the vacancy level of the transmitting buffer with a threshold vacancy level of the transmitting buffer and outputting a second comparison result signal; and an output circuit that outputs the emergency mode signal in response to the first comparison result signal and the second comparison result signal; a first determination circuit for determining if the occupancy level of the receiving buffer is increasing, and outputting a result of the determination as a first signal on a first signal line, the first signal indicating whether the occupancy level of the receiving buffer is increasing; a second determination circuit for determining if the vacancy level of the transmitting buffer is increasing by comparing the vacancy level of the transmitting buffer with a previous transmitting buffer vacancy level that is stored in the second determination circuit and for outputting a result of the determination as a second signal on a second signal line, the second signal indicating whether the vacancy level of the transmitting buffer is increasing; a comparing circuit comparing the vacancy level of the transmitting buffer with the occupancy level of the receiving buffer and outputting a comparison result signal on a comparison result signal line that indicates which of the occupancy level of the receiving buffer and the vacancy level of the transmitting buffer is greater; and a logic circuit coupled to the emergency mode signal line, the first signal line, the second signal line, and the comparison result signal line, and outputting a permission signal to the receiving buffer or the transmitting buffer in response to a combination of the emergency mode signal, the first signal indicating whether the occupancy level of the receiving buffer is increasing, the second signal indicating whether the vacancy level of the transmitting buffer is increasing, and the comparison result signal, the permission signal granting access to the system bus to one of the transmitting buffer and receiving buffer.