EFFICIENT CALCULATION OF A NUMBER OF TRANSITIONS AND ESTIMATION OF POWER DISSIPATION IN SEQUENTIAL SCAN TESTS

摘要

Determining the transition counts at various scan elements of a scan chain (for sequential scan tests) by merely examining the bits of an input vector and the expected results of evaluation (410 - 470). In an embodiment, assuming there are N bits of input vector (with the Nth bit being scanned in first and first bit being scanned in last) and N elements of a scan chain (with the first scan element receiving each bit first), the number of transition at Nth scan element equals an XOR of the Nth bit and the bit stored in the first scan element before scan-in operation. The number of transitions at Pth scan element then equals a sum of (XOR of (P+l)st bit and (Pth bit)) and the number of the transitions at the (P+l)st element. The transitions due to scan out operations can also be similarly determined. The computed number of transitions can be used for determining power dissipation during sequential scan test.