Several different systems and methods are described involving arbitration between asynchronous and isochronous data for access to a data transport resource (e.g., a bus or a memory controller). A first embodiment of a system (e.g., a computer system or a communication system) includes an arbiter coupled to the data transport resource, an asynchronous queue for storing asynchronous data, and an isochronous queue for storing isochronous data. The isochronous queue has a data level range divided into multiple portions. A number of memory locations within the isochronous queue may define the data level range of the isochronous queue. The arbiter arbitrates between the asynchronous queue and the isochronous queue for access to the data transport resource dependent upon the portion of the data level range in which a level of data resides within the isochronous queue. The level of data within the isochronous queue may be a number of memory locations between a write pointer and a read pointer. The arbiter may include a set of arbitration rules, wherein each arbitration rule states conditions used to determine whether data is provided from the isochronous queue or the asynchronous queue. The arbiter may arbitrate between the asynchronous queue and the isochronous queue for access to the data transport resource by: (i) selecting an arbitration rule from the set of arbitration rules dependent upon the portion of the data level range in which the level of data resides within the isochronous queue, and (ii) applying the rule.