Browse Prior Art Database

Compilable ROM signature for built in self test

IP.com Disclosure Number: IPCOM000132626D
Original Publication Date: 2005-Dec-28
Included in the Prior Art Database: 2005-Dec-28
Document File: 4 page(s) / 47K

Publishing Venue

IBM

Abstract

A method is provided to hard code a Bist In Self Test (BIST) signature for a Read Only Memory (ROM) during manufacturing test. Said programming is done via the same software that is used to assemble the ROM and uses the same manufacturing levels that are used to prgram the ROM memory personalization.

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Compilable ROM signature for built in self test

Disclosed is a method to program a ROM personalization signature with the same software that grows and personalizes a ROM and by using the same manufacturing levels as the memory personalization.

When ROMs are manufactured, their contents need to be tested to make sure the array personalization was done properly. A compression scheme is typically used, such as a Serial Input Shift Register (SISR) (see US5,825,785). While a SISR is a compressed value, it still is multiple bits, and each of those bits needs to be examined for correctness. In order to save test time and complexity a single bit "pass/fail" answer is desired. If each memory has a single pass/fail bit, all pass/fail bits can be checked in parallel with simple test logic.

A method is described to internally compare the generated signature produced by BIST and the correct signature, providing a single bit pass/fail answer. Furthermore, the correct signature will be programmed at the same time as the ROM memory contents, by the same tool. No initialization methods will be needed at power on or test initialization to properly set the correct signature. This technique is easier to test because of the lack of initialization and complex compare after BIST.

The new art in this method beyond US5,825,785 is to provide a single pass/fail bit to describe whether or not the ROM memory contents are correct or not. The pass/fail bit is generated by an internal compare in the BIST at its completion between the generated signature and the correct signature. Said correct signature is programmed during manufacturing at the same time using the same mask levels as the memory personalization. An alternative embodiment is to use the exact same programming kernels to program both the memory and the correct signature.

Additional value is gaine...