Digital Systems Testing And Testable Design Solution

When chips are soldered onto a Printed Circuit Board (PCB), testing the connections between them is difficult. JTAG provides a standard "boundary" around the chip's pins, allowing engineers to test board-level interconnects without using physical probes. 4. Automatic Test Pattern Generation (ATPG)

The difficulty of testing any digital system can be distilled into two metrics: (how easily a specific internal node can be set to a desired logic state) and observability (how easily the state of that node can be propagated to a primary output). In a complex sequential circuit, internal state registers act as both barriers and black holes. To test a deep logic path, a tester must sequence the chip through a long chain of clock cycles, a process that is time-consuming and error-prone. digital systems testing and testable design solution

| Metric | Formula / Meaning | |--------|-------------------| | Fault coverage | Detected faults / Total faults | | Test escape | 1 – fault coverage | | Yield | Good chips / total chips | | Defect level | ( (1 - \textyield)^1 - \textfault coverage ) | | Test cost | (Test time × tester hourly rate) + DFT area overhead | When chips are soldered onto a Printed Circuit