Microprocessor with an external command mode for diagnosis and debugging - Patent Review 5479652

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Microprocessor with an external command mode for diagnosis and debugging

United States Patent

5479652

Link to this page

http://www.wikipatents.com/5479652.html

Inventor(s)

Dreyer; Robert S. (Sunnyvale, CA); Alpert; Donald B. (Santa Clara, CA); Modi; Nimish H. (San Jose, CA); Tripp; Mike J. (Forest Grove, OR)

Abstract

A microprocessor is disclosed herein having an external command mode for directly accessing the execution unit, responsive to externally generated commands and instructions. An external instruction path is provided, as well as a conventional processor-driven instruction path. A multiplexer is provided that selects which of the instruction paths is actually supplied to the execution unit. Using the external command mode, the user can examine and modify registers, memory, and I/O space without otherwise affecting their contents. Any instruction executable by the execution unit is executable in the external command mode. Because direct access is provided into the execution unit, there is no implicit updating that would otherwise affect the state of the processor and require saving to an alternate memory. The present invention is implemented with a conventional test access port designed in accordance with the IEEE 1149.1 boundary scan standard, with modification to include an instruction register, a data register, and control logic. The external command mode is applicable to single and multiple pipeline processors. The circuit described herein includes several selectors for selecting between the probe mode and the processor-driven mode of operation, including an external pin, an external command, and a debug exception. For ascertaining if the circuit is in the external command mode, an acknowledge pin is provided to indicate when the execution unit is ready to accept an instruction in the probe model.

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U.S. References

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5353424 Partovi 711/128 Oct,1994	Your vote accepted [0 after 0 votes]		5339437 Yuen 710/261 Aug,1994	Your vote accepted [0 after 0 votes]
5329471 Swoboda Jul,1994	Your vote accepted [0 after 0 votes]		5291604 Kardach 710/261 Mar,1994	Your vote accepted [0 after 0 votes]
5281864 Hahn 327/202 Jan,1994	Your vote accepted [0 after 0 votes]		5276824 Skruhak 712/212 Jan,1994	Your vote accepted [0 after 0 votes]
5276888 Kardach 710/261 Jan,1994	Your vote accepted [0 after 0 votes]		5274834 Kardach 710/260 Dec,1993	Your vote accepted [0 after 0 votes]
5274826 Kardach 710/260 Dec,1993	Your vote accepted [0 after 0 votes]		5265005 Schmidt 700/18 Nov,1993	Your vote accepted [0 after 0 votes]
5263143 Robinson 711/100 Nov,1993	Your vote accepted [0 after 0 votes]		5254942 D'Souza 714/727 Oct,1993	Your vote accepted [0 after 0 votes]
5228039 Knoke 714/28 Jul,1993	Your vote accepted [0 after 0 votes]		5222068 Burchard Jun,1993	Your vote accepted [0 after 0 votes]
5218525 Amasaki Jun,1993	Your vote accepted [0 after 0 votes]		5175853 Kardach 710/260 Dec,1992	Your vote accepted [0 after 0 votes]
5136714 Braudaway 710/260 Aug,1992	Your vote accepted [0 after 0 votes]		5128970 Murphy 375/354 Jul,1992	Your vote accepted [0 after 0 votes]
5125088 Culley 713/400 Jun,1992	Your vote accepted [0 after 0 votes]		5124910 Koumoto 712/234 Jun,1992	Your vote accepted [0 after 0 votes]
5070476 Fujiwara Dec,1991	Your vote accepted [0 after 0 votes]		5056015 Baldwin 703/27 Oct,1991	Your vote accepted [0 after 0 votes]
5036458 Matsushima 712/244 Jul,1991	Your vote accepted [0 after 0 votes]		5036453 Renner 712/16 Jul,1991	Your vote accepted [0 after 0 votes]
5032983 Fu 711/217 Jul,1991	Your vote accepted [0 after 0 votes]		5027273 Letwin 713/600 Jun,1991	Your vote accepted [0 after 0 votes]
4967326 May 712/21 Oct,1990	Your vote accepted [0 after 0 votes]		4949360 Martin 375/354 Aug,1990	Your vote accepted [0 after 0 votes]
4945536 Hancu 714/727 Jul,1990	Your vote accepted [0 after 0 votes]		4914325 Yamada 327/144 Apr,1990	Your vote accepted [0 after 0 votes]
4907150 Arroyo 713/323 Mar,1990	Your vote accepted [0 after 0 votes]		4896289 Svinicki 714/34 Jan,1990	Your vote accepted [0 after 0 votes]
4734882 Romagosa 710/264 Mar,1988	Your vote accepted [0 after 0 votes]		4720811 Yamaguchi 713/601 Jan,1988	Your vote accepted [0 after 0 votes]
4677586 Magar 714/27 Jun,1987	Your vote accepted [0 after 0 votes]		4674089 Poret 714/28 Jun,1987	Your vote accepted [0 after 0 votes]
4644494 Muller 711/152 Feb,1987	Your vote accepted [0 after 0 votes]		4547849 Louie 710/3 Oct,1985	Your vote accepted [0 after 0 votes]
4455622 Loskorn 710/47 Jun,1984	Your vote accepted [0 after 0 votes]		4422141 Shoji 714/30 Dec,1983	Your vote accepted [0 after 0 votes]
4404628 Angelo 709/215 Sep,1983	Your vote accepted [0 after 0 votes]		4403287 Blahut 712/42 Sep,1983	Your vote accepted [0 after 0 votes]
4312066 Bantz Jan,1982	Your vote accepted [0 after 0 votes]		4236204 Groves 712/226 Nov,1980	Your vote accepted [0 after 0 votes]
4200912 Harrington 710/269 Apr,1980	Your vote accepted [0 after 0 votes]		4010448 Bennett 710/269 Mar,1977	Your vote accepted [0 after 0 votes]
3937938 Matthews 714/46 Feb,1976	Your vote accepted [0 after 0 votes]		3805245 Brooks 710/62 Apr,1974	Your vote accepted [0 after 0 votes]
3639911 Frieband 712/228 Feb,1972	Your vote accepted [0 after 0 votes]
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Claims

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What is claimed is:

1. A computer circuit for operating in a processor-driven mode responsive to a series of stored macroinstructions from a computer memory, and also for operating in an external command mode responsive to an externally supplied microinstruction and an externally supplied command, comprising:

a mode selection unit for selecting the external command mode or the processor-driven mode;

an execution unit for executing microinstructions;

a microinstruction multiplexer for providing a selected microinstruction to the execution unit;

a processor-driven instruction path including a decoder for receiving and decoding said stored macroinstructions and decoding them into microinstructions which are then supplied to a first input of the microinstruction multiplexer;

an external instruction path for supplying an externally supplied microinstruction to a second input of the microinstruction multiplexer; and

a control circuit responsive to the mode selection unit for controlling the microinstruction multiplexer to select

during processor-driven operation, a microinstruction resulting from a decoded macroinstruction from the processor-driven instruction path, and

during external command mode operation, an externally supplied microinstruction from the external instruction path.

2. The computer circuit of claim 1 wherein the processor-driven instruction path comprises a decoder that updates the macroinstruction pointer coincident with decoding a macroinstruction.

3. The computer circuit of claim 1 wherein the external instruction path comprises an instruction register coupled to the microinstruction multiplexer, said instruction register for storing an externally supplied microinstruction.

4. The computer circuit of claim 1 wherein the mode selection unit includes a run/stop pin that, when asserted, halts operation of the processor-driven instruction path.

5. The computer circuit of claim 1 wherein the mode selection unit includes control logic, responsive to an externally supplied command, for halting operation of the processor-driven instruction path.

6. The computer circuit of claim 1 wherein the mode selection unit includes a probe mode control register that includes a