Abstract: A method of operating a semiconductor memory device includes receiving a timeout index signal corresponding to a master of the first master group based on a residual capacity of a data buffer of the first master, setting a first timeout value in response to the timeout index signal, and changing an execution order of commands stored in a queue of the semiconductor memory device based on a result of counting the first timeout value and counting a second timeout value corresponding to a master of the second master group.

Abstract: A bus arbiter includes an arbitration stop determining unit and a transaction arbitrating unit. The arbitration stop determining unit generates an arbitration stop signal based upon transaction grouping request signals which indicate whether successive transactions are requested. The transaction arbitrating unit selectively performs an arbitration operation based upon the arbitration stop signal.