Serial scan chain architecture for a data processing system and method of operation
First Claim
1. A data processor having a scan chain architecture, the scan chain architecture comprising:
- a plurality of scan chains wherein each scan chain in the plurality of scan chains has a plurality of serially connected storage elements, each scan chain having a first storage element which has a scan input and a last storage element which has a scan output;
a multiplexer having a plurality of inputs wherein each input in the plurality of inputs is coupled to one scan output from the plurality of scan chains, the multiplexer having a multiplexer output wherein the multiplexer output is selectively coupled to one of the inputs in the plurality of inputs via the multiplexer;
a demultiplexer having a plurality of outputs wherein each output in the plurality of outputs is coupled to one scan input from the plurality of scan chains, the demultiplexer having a demultiplexer input wherein the demultiplexer input is selectively coupled to one output in the plurality of outputs via the demultiplexer; and
an output scan chain having an input coupled to the output of the multiplexer and an output coupled to an output terminal of the data processor, the multiplexer serially coupling the output scan chain to a selected one of the plurality of scan chains to form a total scan chain comprising the selected one of the plurality of scan chains and the output scan chain.
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Abstract
A scan chain architecture which has a controller (10), and a multiplexer (24) is used to route test data through functional units (12, 14, 16, 18, 20, and 22). The controller (10) receives as input a serial data stream from an STDI terminal and demultiplexes this data stream to one of the functional units (six functional units are illustrated in FIG. 1). Each of the functional units is considered as one scan chain and therefore FIG. 1 has six scan chains (one for each functional unit). In addition, a seventh scan chain couples all output flip-flops in each of the functional units together between an output of the MUX (24) and the STDO terminal/pin. Therefore, a serial scan of a data stream can be done through one functional unit, the multiplexer (24) and into the output flip-flops of each function unit to make testing easier to set-up. In addition, various new scan chain cells and low power methods are used herein.
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Citations
28 Claims
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1. A data processor having a scan chain architecture, the scan chain architecture comprising:
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a plurality of scan chains wherein each scan chain in the plurality of scan chains has a plurality of serially connected storage elements, each scan chain having a first storage element which has a scan input and a last storage element which has a scan output; a multiplexer having a plurality of inputs wherein each input in the plurality of inputs is coupled to one scan output from the plurality of scan chains, the multiplexer having a multiplexer output wherein the multiplexer output is selectively coupled to one of the inputs in the plurality of inputs via the multiplexer; a demultiplexer having a plurality of outputs wherein each output in the plurality of outputs is coupled to one scan input from the plurality of scan chains, the demultiplexer having a demultiplexer input wherein the demultiplexer input is selectively coupled to one output in the plurality of outputs via the demultiplexer; and an output scan chain having an input coupled to the output of the multiplexer and an output coupled to an output terminal of the data processor, the multiplexer serially coupling the output scan chain to a selected one of the plurality of scan chains to form a total scan chain comprising the selected one of the plurality of scan chains and the output scan chain. - View Dependent Claims (2, 3)
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4. A data processor comprising:
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a plurality of circuit modules; a plurality of internal storage elements in each circuit module, the plurality of internal storage elements in each circuit module being connected in a serial manner to form an internal scan chain in each circuit module, each internal scan chain having an input and an output wherein the input of each internal scan chain is coupled to a test controller and the output of each internal scan chain is coupled to a multiplexer; and a plurality of output storage elements in each circuit module, the plurality of output storage elements in each circuit module being different from the plurality of internal storage elements in each circuit module, the plurality of output storage elements in each circuit module being connected in a serial manner to form an output scan chain which is continuous through each circuit module, the output scan chain in each circuit module having an input and an output wherein the inputs and outputs of each of the output scan chains are coupled so that all the output scan chains in the circuit modules are coupled in a serial manner wherein the multiplexer selectively couples one internal scan chain and at least one output scan chain together in a serial manner to a scan data output terminal. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A data processor comprising:
a scan chain having a plurality of serially connected storage cells, each serially connected storage cell comprising; a storage element having a clock input for receiving a clock signal, a data input, and a data output; a first multiplexer having a first input coupled to receive a serial stream of data, a second input, a select input for receiving a select control signal, and an output coupled to the data input of the storage element; a second multiplexer having a first input coupled to the output of the storage element, a second input coupled to a data input, a select input, and an output coupled to the first input of the first multiplexer; and a logic gate having a first input for receiving an enable signal, a second input for receiving a speed path control signal, and an output coupled to the select input of the second multiplexer.
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23. A method for providing a serial data stream to a data processor, the method comprising the steps of:
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providing an address to a test controller, the address coupling one serial scan chain from a plurality of scan chains internal to the data processor to an input terminal, each scan chain in the plurality of scan chains having a plurality of serially connected storage elements, the serially connected storage elements of each scan chain defining a circuit module boundary wherein all the serially connected storage elements of each scan chain are within the circuit module boundary; using the address to couple the one serial scan chain selectively to an output scan chain wherein the output scan chain is a serially connected plurality of storage elements from a plurality of different circuit modules defined by the circuit module boundaries; and serially shifting the serial data stream into both the output scan chain and the one serial scan chain via the input terminal. - View Dependent Claims (24, 25, 26, 27, 28)
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Specification