Browse Prior Art Database

Built-In Self-Test (BIST) and user logic sharing method using FPGA

IP.com Disclosure Number: IPCOM000021136D
Original Publication Date: 2003-Dec-26
Included in the Prior Art Database: 2003-Dec-26
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Abstract

BIST is used to test SRAM, DRAM, and other hard macros. After wafer/module test, BIST is not used. If BIST can be replaced by an user logic when normal function, the cell count can be reduced. This document shows how to share BIST and a user logic to embedded FPGA.

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Built-In Self-Test (BIST) and user logic sharing method using FPGA

Some ASIC provides embedded FPGA. A FPGA is used to implement user logic after chip manufacturing. User logic, which is implemented into embedded FPGA, is transferred via JTAG port, serial or parallel interface after power on reset. During wafer/module test no logic is written to embedded FPGA. On the other hand, BIST (Built-In-Self-Test) is used to test SRAM, DRAM, and processors during wafer/module test. The BIST is only used to test whether LSI is good or bad. After wafer/module test, BIST is not needed anymore. If BIST is implemented into embedded FGPA during wafer/module test and after the test, BIST is replaced by user logic. Chip area for BIST can be eliminated and chip cost can be reduced. This document shows how to share BIST and user logic into embedded FPGA. Fig 1 shows the relationship between SRAM and BIST. The test logic is embedded in BIST to test SRAM. To test all memory elements in SRAM, such as checkerboard, stripe, and unique address pattern are applied to the SRAM. These logic are embedded in BIST and a result is automatically checked by BIST and when all tests are completed, pass/fail signal is sent to a LSI tester. The BIST is used to test whether LSI is good or bad, after wafer/module test, the BIST will not be used.

ASIC

BIST

SRAM

Fig 1

Fig 2 shows the detail description of this method. In Fig2, the configuration logic is used to transfer data to the embedded FPGA. At wafer/module test, a LSI tester writes BIST logic which checks SRAM function to the FPGA. The address and d...