Phase shifter with reduced linear dependency
First Claim
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1. A method of creating a pseudo-random pattern generator used to generate test patterns in a built-in self-test framework, comprising:
- generating a linear feedback shift register including multiple flip-flops coupled in a ring structure with feedback connections between the flip-flops and with output taps that provide a pseudo-random pattern; and
generating a phase shifter coupled to the linear feedback shift register, the phase shifter including multiple XOR or XNOR gates, wherein generating the phase shifter includes storing loading information on each output tap of the linear feedback shift register and coupling the output taps to the XOR or XNOR gates of the phase shifter by ensuring that the output taps are not used if their respective loading exceeds a predetermined limit.
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Abstract
A method is disclosed for the automated synthesis of phase shifters—circuits used to remove effects of structural dependencies featured by pseudo-random test pattern generators driving parallel scan chains. Using a concept of duality, the method relates the logical states of linear feedback shift registers (LFSRs) and circuits spacing their inputs to each of the output channels. The method generates a phase shifter network balancing the loads of successive stages of LFSRs and satisfying criteria of reduced linear dependency, channel separation and circuit complexity.
165 Citations
18 Claims
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1. A method of creating a pseudo-random pattern generator used to generate test patterns in a built-in self-test framework, comprising:
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generating a linear feedback shift register including multiple flip-flops coupled in a ring structure with feedback connections between the flip-flops and with output taps that provide a pseudo-random pattern; and generating a phase shifter coupled to the linear feedback shift register, the phase shifter including multiple XOR or XNOR gates, wherein generating the phase shifter includes storing loading information on each output tap of the linear feedback shift register and coupling the output taps to the XOR or XNOR gates of the phase shifter by ensuring that the output taps are not used if their respective loading exceeds a predetermined limit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 12, 13)
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9. An apparatus to generate test patterns in a built-in self-test framework, comprising:
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a linear feedback shift register including multiple flip-flops coupled in a ring structure with feedback connections between the flip-flops and with output taps that provide a pseudo-random pattern; and a phase shifter coupled to the linear feedback shift register, the phase shifter including multiple XOR or XNOR gates coupled to the output taps of the linear feedback shift register, wherein the number of XOR or XNOR gates coupled to the output taps is substantially equal in number. - View Dependent Claims (10)
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11. A method of creating a pseudo-random pattern generator used to generate test patterns in a built-in self-test framework, comprising:
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generating a linear feedback shift register including multiple flip-flops coupled in a ring structure with feedback connections between the flip-flops and with output taps that provide a pseudo-random pattern; and generating a phase shifter including multiple XOR or XNOR gates, wherein generating the phase shifter includes distributing the connections between the XOR and XNOR gates and the output taps so as to achieve balanced loading on the output taps. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification