Scan interface

Abstract

A scan interface for an integrated circuit includes a scan clock and a scan mode signal. The scan mode signal is indicative of whether or not scan is active, and may be used by dedicated scan circuitry in integrated circuit. Such circuitry may be inactive if the scan mode indicates that scan is inactive, and active if the scan mode indicates that scan is active. For example, the scan circuitry may not toggle is scan is inactive. The scan circuitry may present a reduced load to functional circuitry if scan is inactive. In some embodiments, static and dynamic scan circuits are included for use with static and dynamic logic circuits, respectively.

1 . An integrated circuit having a scan interface, the scan interface consisting of: 
 a scan mode signal provided on a scan mode pin of the integrated circuit, wherein dedicated scan circuits within the integrated circuit are coupled to receive the scan mode signal and, responsive to a state of the scan mode signal indicating that scan is inactive, the dedicated scan circuits are inactive, and wherein, responsive to the state of the scan mode signal indicating that scan is active, the dedicated scan circuits are active;    a scan in signal provided on a scan in pin of the integrated circuit for providing scan data to the integrated circuit;    a scan out signal provided on a scan out pin of the integrated circuit for providing scan data from the integrated circuit; and    a scan clock signal provided on a scan clock pin of the integrated circuit, the scan clock separate from a functional clock provided to the integrated circuit, wherein state elements within the integrated circuit are configured to capture scan values responsive to the scan clock signal.    
   
   
       2 . The integrated circuit as recited in  claim 1  wherein the dedicated scan circuits do not toggle when inactive.  
   
   
       3 . The integrated circuit as recited in  claim 1  wherein the dedicated scan circuits present a reduced load to functional circuitry in the integrated circuit when inactive.  
   
   
       4 - 20 . (canceled)