Abstract: A bus protocol for a split bus (50, 60) where each device (10, 20, 30) coupled to the bus has an age-based queue (12, 24, 34) of pending transactions. Queues are updated as transactions are executed. A central arbiter (40) has a copy of each device's queue (44). A priority transaction is determined from among all the queues in the arbiter. A data transaction index (DTI) is broadcast during the data tenure to all devices indicating the position in the queue of the next transaction. The index allows out-of-order data transfers without the provision of a static tag during the address tenure. Queues maintain a history of pending transactions. In one embodiment, each device receives a separate data bus grant (DBG), allowing a single provision of the index to both a source and a sink device.

Abstract: A method of transferring data between a slave device (20) in communication with a processor interface bus (34) where the processor interface bus is in communication with a master device (12) including receiving an address from the processor interface bus (34) where the address was provided by the master device (block 302). A first signal is asserted (blocks 318 and 324) on the processor interface bus (34) to indicate that the slave device (20) is servicing a data transfer transaction. A second signal is asserted (block 320) on the processor interface bus (34) to indicate whether data to be transferred using the processor interface bus (34) is to be stored in main memory (36) by a main memory controller (32) in communication with the processor interface bus (34). The data is transferred (block 326) between the slave device (20) and the processor interface bus (34).