METHOD AND STRUCTURE FOR INTERRUPT POLLING SIGNAL BANDWIDTH ALLOCATION IN UNIVERSAL SERIAL BUS (USB) SYSTEM

A Universal Serial Bus (USB) controller includes an allocation unit configured to allocate bandwidths to a plurality of nodes in a polling list, each node being capable of storing at least one descriptor representing a respective polling signal. The nodes are arranged in a binary tree structure having a plurality of leaf nodes, a root node, and at least one level of intermediate nodes which are successor nodes for the leaf nodes and predecessor nodes for the root node. The allocation unit is configured to store variables P and S for each node, where P is a maximum bandwidth of polling signals entering a node from predecessor nodes, and S is a sum of bandwidths of polling signals represented by descriptors stored in the node and all successor nodes thereof. It assigns a new device to a node such that a maximum value of P+S for the nodes at each level is minimized. The allocation unit adds a descriptor representing a new polling signal to a node in a specified level which has a minimum value of P+S. After adding a descriptor to a node, the allocation unit alters values of S for the node and all predecessor nodes thereof by adding the bandwidth of the new polling signal represented by the descriptor to the values of S, and alters values of P for successor nodes thereof in accordance with the bandwidth of the polling signal represented by the descriptor.