BIST and Scan Design

Built-in self-test (BIST) circuitry, along with scan circuitry, greatly enhances a design’s testability. BIST leaves the job of testing up to the device itself, eliminating or minimizing the need for external test equipment. A discussion of BIST and the BIST process is provided in the Built-in Self-Test Process Guide. Scan circuitry facilitates test generation and can reduce external tester usage. There are two main types of scan circuitry:
Internal Scan and boundary scan
Internal scan (also referred to as scan design) is the internal modification of your design’s circuitry to increase its testability.
Boundary Scan While scan design modifies circuitry within the original design, boundary scan adds scan circuitry around the periphery of the design to make internal circuitry on a chip accessible via a standard board interface. The added circuitry enhances board testability of the chip, the chip I/O pads, and the interconnections of the chip to other board circuitry.