A new approach to testing based on boundary scan is discussed. This technique gives access to individual chip pins by including a little standardized circuitry and a test access port (TAP) on every IC. Boundary scan basics are reviewed, and three principal types of tests that can be performed with the boundary-scan register are described. They are: interconnect tests, using the EXTEST (external test) instruction; chip tests, using the INTEST instruction; and sampling, using the SAMPLE instruction.