VLSI Concept · DFT
Scan Chains & ATPG
Turn every flip-flop into a shift register, just for testing.
In scan mode, all flip-flops are reconfigured into one long shift register (scan chain), letting automated test equipment shift in a known test pattern, run one clock cycle in normal mode, then shift out the result to compare against the expected response — this is how every manufactured chip gets checked for defects.