22. The method of claim 16 , wherein the memory structure is configured to hold a record for each of a plurality of nodes in the lexical tree, the record including said states, a previous node identifier for identifying a previous node in the lexical tree, and information indicating whether said each node is a previous node for another node stored in said memory structure, the speech recognition circuit including a circuit to identify a first node which is not a previous node of another record, and to provide a new data record corresponding to a new node, the new node being the next node after the first node in the lexical tree, using a score associated with the first node.
16. A method of speech recognition, comprising providing state identifiers which identify states corresponding to nodes or groups of adjacent nodes in a lexical tree, the lexical tree comprising a model of words; providing scores corresponding to said state identifiers; receiving and storing state identifiers identified by node identifiers identifying a node or group of adjacent nodes in a memory structure; looking up said memory structure to identify particular state identifiers; reading of the scores corresponding to the state identifiers; receiving score updates corresponding to particular state identifiers from a score update generating circuit which generates the score updates using audio input; modifying said scores by adding said score updates to said scores; writing back of the scores to the memory structure after modification of the scores; and selecting at least one node or group of adjacent nodes of the lexical tree according to said scores.