Digital Systems Testing And Testable Design Solution

| Action | Benefit | |--------|---------| | Use scan chains | Convert sequential to combinational test | | Avoid asynchronous resets | Prevent race conditions during scan | | Add test points | Increase observability/controllability | | Use boundary scan | Board-level test and debug | | Insert BIST | On-chip self-test for field/AT-speed | | Run ATPG early | Estimate fault coverage before layout | | Follow DFT guidelines | Reduce test cost and improve yield |

TDI (Test Data In), TDO (Test Data Out), TMS , TCK , and optional TRST (Test Reset).

At-speed testing requires careful handling of clock networks and may cause over-testing (testing paths that are never sensitized in functional mode). New fault models like (defects inside standard cells) are gaining traction.

Chip generates its own test vectors and compresses responses. digital systems testing and testable design solution

┌────────────────────────────────────────┐ │ BIST Chip │ │ ┌──────┐ ┌──────────┐ ┌──────┐ │ │ │ LFSR │ ───> │ Circuit │ ─>│ MISR │ │ │ │(TPG) │ │Under Test│ │(ORA) │ │ │ └──────┘ └──────────┘ └──────┘ │ └────────────────────────────────────────┘ Logic BIST (LBIST)

Detecting a fault early saves significant capital. The industry follows the : a fault costs ten times more to find and fix at each subsequent stage of production:

Design for Testability (DFT) is not a single technique but a philosophy. It encompasses a set of hardware and software techniques that deliberately alter the design of a digital system to make it easier, faster, and more thorough to test. The golden rule of DFT is: Testability must be designed in, not added on. | Action | Benefit | |--------|---------| | Use

Create a sensitive path through the remaining logic gates so the faulty value can travel all the way to an external output pin.

: a systematic approach that integrates test features directly into the hardware from day one. Why We Can’t Just "Plug and Play"

Deep sub-micron technologies introduce defects within individual transistors: Chip generates its own test vectors and compresses responses

Test data volume for large SoCs can reach terabytes. Compression reduces this by 10x to 100x.

The shift away from monolithic silicon dies toward heterogeneous (using 2.5D and 3D stacking via silicon interposers) introduces unique test challenges: