Out in Front

Chip BIST moves to MCMs and pc boards

You use traditional chip built-in self-test (BIST) only for on-chip memories and embedded blocks. LogicVision has gone a step further with its new memory controller, which generates BIST for discrete multichip-module (MCM) and board-based memory chips. For these chips, memBIST-XT generates test data and expected responses and captures and compares actual responses.

The software embeds a controller into an ASIC or FPGA chip, using about 1000 logic gates, that interfaces with the memory. You control memBIST-XT either through pins on the ASIC or FPGA on which the BIST logic resides or from a pc board's IEEE 1149.1-compliant test-access-port controller. The BIST controller runs at full system speed, allowing you to test memory at normal speed. Along with the control logic, memBIST-XT produces a BIST "collar," an interface between the controller and external memories. The collar includes multiplexer logic for switching between functional and control signals.

With memBIST-XT, you input design information about the memory cluster you want to test. The software automatically generates the BIST controller in Verilog or VHDL. The software provides the HDL-synthesis script, which is appended to the synthesis script for the chip containing the controller logic. The software also includes a testbench to verify the functionality of the generated BIST controller and collar.

The memBIST-XT program implements several variations of the "marching" test pattern, with user-programmable read and write access sequences. The se-quences—read/write, read/write/read, read/write/read/read, and read/write/read/write—let you test many memory types, including SRAM, DRAM, and synchronous DRAM. LogicVision benchmarked the test time for a 16316-Mbyte DRAM, configured in four memory slots, at 262 msec for the read/write sequence. The software's algorithms test for stuck-at faults, shorts, and coupling faults for bit lines, data buses and address lines. The controller also tests for cell-based problems, such as stuck-at faults.

The memBIST-XT program will be available on Hewlett-Packard and Sun workstations in the first quarter of next year. License fees start at $20,000 per design for as many as three designs and decrease for additional designs.—by Jim Lipman

LogicVision, San Jose, CA. (408) 453-0146, fax (408) 467-1180, http://www.lvision.com.