scan path

scan path

(circuit design) A technique used to increase thecontrollability and observability of a logic circuit byincorporating "scan registers" into the circuit. Normallythese act like flip-flops but they can be switched into a"test" mode where they all become one long shift register.This allows data to be clocked serially through all the scanregisters and out of an output pin at the same time as newdata is clocked in from an input pin.

Using this technique, the state of certain points in thecircuit can be examined and modified at any time by suspendingnormal operation and switching to test mode. If the scan pathis placed adjacent to the circuit's input and output pins thenthis is known as "boundary scan".