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US 6,205,536 B1Granted
Combined Instruction and address caching system using independent buses
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorToyohiko Yoshida
Life of this patent
Estimating the term…
Abstract
A microprocessor and a data processor therefor which have separate data and instruction buses, and wherein a data address and an instruction address are output over a single address bus in a time-shared manner, thereby allowing a data access and an instruction access to be pipelined without the need for separate address buses between the microprocessor and caches holding data and instructions.
Claims12
An apparatus for data processing, comprising:
- a data memory, having a data address input;
- an instruction memory, having an instruction address input;
- a processor, having an address output, said processor overlapping first and second access cycles, said first and second access cycles being either a data access followed by an instruction access or an instruction access followed by a data access;
- means for data and instruction access which reads data from or writes data to said data memory during a data access cycle and which reads instructions from said instruction memory during an instruction access cycle;
- an address bus coupling said address output of said processor to said data address input of said data memory and said instruction address input of said instruction memory;
- a data bus coupling said processor and said data memory, whereby data are carried between said processor and said data memory;
- an instruction bus coupling said processor and said instruction memory, whereby instructions are carried from said instruction memory to said processor;
- a control bus coupling said processor, said data memory, and said instruction memory, said control bus comprising a plurality of control signals, said control signals comprising at least:
- an access type signal from said processor to said data memory or said instruction memory, said access type signal indicating which of a data access and an instruction access is being requested by said processor;
- a data transfer end signal from said data memory to said processor, said data transfer end signal indicating the completion of a data transfer over said data bus;
- and
- an instruction transfer end signal from said instruction memory to said processor, said instruction transfer end signal indicating the completion of an instruction transfer over said instruction bus;
- means for controlling data and instruction access, whereby said processor overlaps said first and second access cycles and completes said second access cycle before said first access cycle is complete, said processor, during said first access cycle, always releasing said address bus before said first access cycle completes,
- a data address latch, coupled to said data address input for latching contents of said address bus while a valid data address is present on said address bus and until said data memory completes an access of a data memory location addressed by said contents of said address bus;
- and
- an instruction address latch, coupled to said instruction address input for latching contents of said address bus while a valid instruction address is present on said address bus and until said instruction memory completes an access of an instruction memory location addressed by said contents of said address bus.
13 more elements
An apparatus for data processing, comprising:
- a data memory, having a data address input;
- an instruction memory, having an instruction address input;
- a processor, having an address output, said processor overlapping first and second access cycles, said first and second access cycles being either a data access followed by an instruction access or an instruction access followed by a data access;
- means for data and instruction access which reads data from or writes data to said data memory during a data access cycle and which reads instructions from said instruction memory during an instruction access cycle;
- an address bus coupling said address output of said processor to said data address input of said data memory and said instruction address input of said instruction memory;
- a data bus coupling said processor and said data memory, whereby data are carried between said processor and said data memory;
- an instruction bus coupling said processor and said instruction memory, whereby instructions are carried from said instruction memory to said processor;
- a control bus coupling said processor, said data memory, and said instruction memory comprising a plurality of control signals, said control signals comprising at least:
- an access type signal from said processor to said data memory or said instruction memory, said access type signal indicating which of a data access and an instruction access is being requested by said processor;
- a data transfer end signal from said data memory to said processor, said data transfer end signal indicating the completion of a data transfer over said data bus;
- and
- an instruction transfer end signal from said instruction memory to said processor, said instruction transfer end signal indicating the completion of an instruction transfer over said instruction bus;
- means for controlling data and instruction access, whereby said processor overlaps said first and second access cycles and completes said second access cycle before said first access cycle is complete, said first and second access cycles being either a single data word access followed by a single instruction word access or a single instruction word access followed by a single data word access;
- a data address latch, coupled to said data address input for latching contents of said address bus while a valid data address is present on said address bus and until said data memory completes an access of a data memory location addressed by said contents of said address bus;
- and
- an instruction address latch, coupled to said instruction address input for latching contents of said address bus while a valid instruction address is present on said address bus and until said instruction memory completes an access of an instruction memory location addressed by said contents of said address bus.
13 more elements
Dependencies are inferred from the claim text.