Credence Systems Corporation

Hrant Marandjian

Yervant D Lepejian

Lawrence A Kraus

Hovhannes Ghukasyan

John M Caywood

A BIST function is provided in which both the routing area devoted to the test signals and the area devoted to the circuits required to implement the BIST routines are minimized, while also including the ability to test a plurality of embedded memories at full speed in parallel. Testing the memories at full speed both reduces test time and improves the quality of the testing.

Method and apparatus for built-in self test of integrated circuits

A built-in self test (BIST) circuit for an integrated circuit tests one or more embedded memories by writing data to each memory address, reading it back out, and then comparing the input and output data to see if they match. The BIST circuit includes one or more data generators for supplying a sequence of data to be written to the various addresses of each memory and one or more identical address generators, each for supplying addresses to a separate embedded memory during read and write operations. Though the memories may have differently sized address spaces, all address generators generate a similar address sequence having a range of address values as large or larger than the address space of the largest memory. During each memory write cycle, a separate filter checks the address output of each address generator to determine whether the address is within the address space of the corresponding memory. If so, the BIST circuit writes the current data output of a data generator to that address of the memory. If not, the BIST circuit ignores the current address and data outputs of the address and data generators and repeats the write operation it performed during a next preceding memory write cycle, writing the same data to the same valid memory address. The BIST circuit makes a similar address substitution during write operation. This allows the BIST circuit to use identical address generators for all memories regardless of the size of the memory being tested.

Efficient built-in self test for embedded memories with differing

A method and circuit are provided for generating a minimum-sized address filter to detect when the address space of an embedded memory having a smaller address space than another larger embedded memory is being exceeded. The method includes decomposing a maximum address into alternating sequences of consecutive binary ones (1's) and zeros (0's), discarding a final sequence if it contains binary 1's, and generating a filter circuit from a filter function formed from the alternating sequences of consecutive binary 1's and 0's. A built-in self test (BIST) circuit incorporating the address filter provides the ability to test a plurality of embedded memories at full speed in parallel. A computer system including a computer program for generating the filter circuit may also be provided.

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Yerevan, Armenia

Hrant Marandjian