High performance processor interface between a single chip processor and off chip memory means having a dedicated and shared bus structure
First Claim
1. A high performance interface between a single chip processor, constituting part of a reduced instruction set computer (RISC) system, and a set of off chip devices, including memory means, said processor having a plurality of different off chip memory access protocols, wherein said interface comprises:
- (a) a shared processor output address bus, coupling said processor and said off chip memory means, for carrying both instruction and data access signals being transmitted by said processor to said off chip memory means;
(b) a dedicated processor input instruction bus, coupling said processor and said off chip memory means, for carrying only instruction signals being transmitted by said off chip memory means to said processor; and
(c) a bidirectional data bus coupling said processor and said off chip memory means, for carrying data signals being transmitted by said off chip memory means to said processor and for carrying data signals being transmitted by said processor to said off chip memory means, which in at least one of said protocols operates simultaneously with said dedicated processor instruction bus.
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Accused Products
Abstract
Methods and apparatus for realizing a high performance interface between a processor, constituting part of a reduced instruction set computer (RISC) system, and a set of devices, including memory means. According to the invention, the interface includes three independent buses. A shared processor output bus, a processor input instruction bus, and a bidirectional data bus. The shared processor output address bus coupled the processor and the computer'"'"'s memory. This bus carries both instructon and data access signals being transmitted by the processor to the memory. The processor input instruction bus also couples the processor and the computer'"'"'s memory means, but carries instruction signals being transmitted from the memory to the processor. The bidirectional data bus provides a signal path for carrying data signals being transmitted by the memory to the processor and vice-a-versa. The novel interface uses demultiplexed buses for simpler timing and uses the separate data and instruction buses to provide extremely high transfer rates at a reasonable cost. The shared address bus accommodates pipelined and burst mode processor protocols with the burst mode protocol allowing concurrent data and instruction transfers. Methods and apparatus for controlling the buses and reporting bus status, etc., are also part of the invention and facilitate the implementation of features that include status reporting, handshaking between devices and the RISC processor, and bus arbitration.
125 Citations
34 Claims
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1. A high performance interface between a single chip processor, constituting part of a reduced instruction set computer (RISC) system, and a set of off chip devices, including memory means, said processor having a plurality of different off chip memory access protocols, wherein said interface comprises:
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(a) a shared processor output address bus, coupling said processor and said off chip memory means, for carrying both instruction and data access signals being transmitted by said processor to said off chip memory means; (b) a dedicated processor input instruction bus, coupling said processor and said off chip memory means, for carrying only instruction signals being transmitted by said off chip memory means to said processor; and (c) a bidirectional data bus coupling said processor and said off chip memory means, for carrying data signals being transmitted by said off chip memory means to said processor and for carrying data signals being transmitted by said processor to said off chip memory means, which in at least one of said protocols operates simultaneously with said dedicated processor instruction bus. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A high performance interface between a single chip processor, constituting part of a reduced instruction set computer (RISC) system, and a set of off chip devices, including off chip memory means, said processor having a plurality of different off chip memory access protocols, wherein said interface comprises:
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(a) a shred processor output address bus, coupling said processor and said off chip memory means, for carrying both instruction and data access signals being transmitted by said processor to said off chip memory means; (b) a dedicated processor input instruction bus, coupling said processor and said off chip memory means, for carrying only instruction signals being transmitted by said off chip memory means to said processor; (c) a bidirectional data bus coupling said processor and said off chip memory means, for carrying data signals being transmitted by said off chip memory means to said processor and for carrying data signals being transmitted by said processor to said off chip memory means, which in at least one of said protocols operates simultaneously with said dedicated processor instruction bus; and (d) a plurality of signal paths used for carrying signals belonging to a set of processor and off chip device generated signals which are used to control said buses. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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25. A method for achieving a high performance interface between a single chip processor constituting part of a reduced instruction set computer (RISC) system, and a set of off chip devices, including off chip memory means, said processor having a plurality of different off chip memory access protocols, comprising the steps of:
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(a) transmitting instruction and data access signals from said processor to said off chip memory means utilizing a shared address bus; (b) transmitting instructions from said off chip memory means to said processor via a dedicated instruction bus, independent of said shared address bus; and (c) transmitting data between said processor and said off chip memory means via data bus which is independent of both said dedicated instruction bus and said address bus and which in at least one of said protocols operates simultaneously with said dedicated processor instruction bus. - View Dependent Claims (27, 32, 33, 34)
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- 26. A method as set forth in claim 26 further comprising the step of transmitting over a plurality of signal paths, signals belonging to a set of processor and off chip device generated signals which are used to control said buses.
Specification