Motorola Corporation

David M Menard

Donald L Tietjen

Frank C Galloway

Nancy G Woodbridge

Ronny L Arnold

Juan Guillermo Revilla

A bus interface unit within a processor ensures a delay period after the occurrence of a read operation to avoid bus contention on a multiplexed bus, When there is a requirement for a back-to-back read or write operation subsequent to the read bus cycle on a multiplexed bus it is important to allow devices, such as memory, sufficient time to reset after transmission of data. To avoid the bus contention problem that occurs after a read bus cycle, i.e, prevent a next address on the bus until the bus is in a tri-state condition, one embodiment inserts idle clock cycles subsequent to a read but not subsequent to a write, The present invention avoids bus contention on a multiplexed bus while providing flexibility in interfacing with a variety of memory devices, and providing a flexible processor design.

System and method for avoiding bus contention on a multiplexed bus by

A data processing system (10) having a bus controller (5) that uses a communication bus (22) which adapts to various system resources (7) and is capable of burst transfers. In one embodiment, the processor core (2) and system resources (7) supply control signals supplying required parameters of the next transfer. The bus controller is capable of transferring operands and/or instructions in incremental bursts from these system resources. Each transfer data burst has an associated unique access address where successive bytes of data are associated with sequential addresses and the burst increment equals the data port size. The burst capability is dependent on the ability of system resource (7) to burst data and can be inhibited with a transfer burst inhibit signal. The length of the desired data is controlled by a sizing signal from the core (2) or from cache and the increment size is supplied by the resource (7).

Method and apparatus for bursting operand transfers during dynamic bus

A data processing system (10) having a bus controller (5) and a multiplexed communication bus (22) and provides a portion of the valid address information during the data phase. In one embodiment, in response to an address extension control signal, the bus controller (5) allocates the communication bus (22) to provide the address extension on conductors not needed for data, reducing the need for address latch circuitry. In an alternate embodiment, the bus controller (5) provides burst transfers where the processor core (2) increments a portion of each address with each data in the burst. For such burst transfers, the length of the desired data is controlled by a sizing signal (42) from the core (2) or from cache and the increment size is supplied by the system resource (7).

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Austin, TX, United States of America

David M Menard