Hitachi, Ltd.

Stmicroelectronics Gmbh

Margaret Rose Gearty

Chih-Jui Peng

David Alan Edwards

Anthony Willis Rich

Naohiko Irie

Glenn Ashley Farrall

Bernard Ramanadin

Atsushi Hasegawa

Tony Lee Werner

An microcomputer is provided including a processor and a debug circuit including a dedicated link which transfers information between the processor and debug circuit to support debugging operations. In one aspect, the processor provides program counter information, which is stored in a memory-mapped register of the debug circuit. The program counter information may be a value of the processor program counter at a writeback stage of a processor pipeline. Also, trace information including message information is transferred in a non-intrusive manner over the dedicated link. In one aspect, the microcomputer is implemented as a single integrated circuit.

Interface for transferring debug information

Apparatus and method for shadowing processor information

In a computer system having a central processing unit (CPU) execution pipeline and a floating point unit (FPU) execution pipeline, the CPU execution pipeline including a CPU decoder pipestage and the FPU execution pipeline including an FPU decoder pipestage, the method including the steps of, (a) sending a first instruction to the CPU decoder pipestage, (b) sending the first instruction to the FPU decoder pipestage, (c) generating a signal indicating that the first instruction has been accepted by the CPU decoder pipestage, (d) generating a signal indicating that the first instruction has been accepted by the FPU decoder pipestage, (e) sending a second instruction to the CPU decoder pipestage in response to step (d), and (f) sending a second instruction to the FPU decoder pipestage in response to step (c). A corresponding apparatus is also provided.

Microcomputer/floating point processor interface and method

A computer system having a central processing unit (CPU) execution pipeline and a floating point unit (FPU) execution pipeline, the CPU pipeline including a plurality of pipestages and the FPU pipeline including a plurality of pipestages, wherein each CPU pipestage in the CPU pipeline has a corresponding pipestage in the FPU pipeline, a method of synchronizing operation of the CPU pipeline and the FPU pipeline, the method including the steps of (a) receiving an instruction in a first CPU pipestage, (b) receiving the instruction in a corresponding first FPU pipestage, (c) processing the instruction in the first CPU pipestage, (d) processing the instruction in the first FPU pipestage, (e) generating, by the first CPU pipestage, a first signal indicating that the instruction has been processed by first CPU pipestage and is ready to proceed to a second pipestage in the CPU pipeline, (f) generating by the first FPU pipestage, a second signal indicating that the instruction has been processed by the first FPU pipestage and is ready to proceed to a second pipestage in the FPU pipeline, (g) sending the instruction from the first CPU pipestage to the second pipestage in the CPU pipeline, (h) sending the instruction from the first FPU pipestage to the second pipestage in the FPU pipeline, (i) wherein the second pipestage in the CPU pipeline responds to the second signal to send the instruction to a third pipestage in the CPU pipeline, and (j) wherein the second pipestage in the FPU pipeline responds to the first signal to send the instruction to a third pipestage in the FPU pipeline. A corresponding apparatus is also provided.

Synchronized instruction advancement through CPU and FPU pipelines

A method for low latency access to the control space. A pipeline processor executes instructions in multiple stages including a decode stage, one or more execution, stages, and a writeback stage. A control space access instruction includes a first field containing a control register specifier and a second field containing a general purpose register specifier. The decode stage is configured to decode the first and second fields and place the decoded contents on a global operand bus. The specified control register is addressed from the global operand bus while the access instruction is in decode. In the case of a read instruction, the addressed control register places its contents on the global operand bus while the instruction remains in decode. In the case of a write instruction, the general purpose register is addressed during the execution stage and its contents placed on the global operand bus during the writeback stage such that the contents of the addressed general purpose register are moved to the addressed configuration register during the writeback stage.

Mechanism for fast access to control space in a pipeline processor

A processor having an execution pipeline and a cache memory including a plurality of cache blocks with instruction words held in selected ones of the cache blocks. An ICBI address buffer is provided for holding addresses of instruction cache blocks to be invalidated by ICBI instructions pending in the processor's execution pipeline. An instruction cache controller coupled to the cache memory generates cache accesses to invalidate specified cache blocks in response to receiving buffered addresses from the ICBI address buffer. Preferably the cache accesses serve to commit ICBI instructions to the instruction cache asynchronously with respect to the processor's execution pipeline.

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Bath, United Kingdom

Margaret Rose Gearty