Method and apparatus for synthesizing circular decompressors

A system, comprising:

• a tester configured to generate test data;
• and
• an integrated circuit comprising:
• a set of scan chains;
• and
• a decompressor circuit to decompress the test data and shift the decompressed test data into the set of scan chains during a plurality of shift cycles, wherein the decompressor circuit further comprises two or more shift registers configured to shift in the test data;
• wherein each of the two or more shift registers includes two or more sequential elements configured such that a scan chain receives inputs from at most one sequential element in each of the two or more shift registers;
• and
• wherein at least one shift register in the set of shift registers is configured as a circular shift register.

A method for constructing a decompressor circuit for decompressing test data from a tester and routing the decompressed test data into a set of scan chains within a circuit under test, the method comprising:

• receiving the set of scan chains;
• receiving two or more shift registers configured to shift in the test data from the tester;
• wherein each of the two or more shift registers includes two or more sequential elements configured such that a scan chain in the set of scan chains receives inputs from at most one sequential element in each of the two or more shift registers;
• and
• wherein at least one shift register in the two or more shift registers is configured as a circular shift register;
• and
• coupling the set of scan chains to the two or more shift registers to form a logic network between the two or more shift registers and the set of scan chains.