Granted Patent B2

US 7,502,978 · App. 11/314,570 · Granted Mar 10, 2009

Abstract

Claims (26)

1. A method for reconfiguring a scan chain, comprising:

providing a first scan chain of flip-flops;

determining whether the first scan chain is to be operated in either a normal mode or a rotate mode;

providing inputs to the flip-flops in sequential order such that a first of the flip-flops receives an input prior to a second of the flip-flops if it is determined that the first scan chain is to operate in the normal mode; and

providing inputs to the flip-flops such that the first of the flip-flops receives an input subsequent to the second of the flip-flops if it is determined that the first scan chain is to operate in the rotate mode.

2. The method of claim 1 , wherein the first scan chain comprises multiple segments of flip-flops, the first and second flip-flops corresponding to a first of the segments; and

wherein determining whether the first scan chain is to be operated in either a normal mode or a rotate mode comprises:

determining whether the first segment is to be operated in either a normal mode or a rotate mode and whether a second of the segments is to be operated in either a normal mode or a rotate mode.

3. The method of claim 1 , wherein, in providing inputs to the flip-flops such that the first of the flip-flops receives an input subsequent to the second of the flip-flops, the first scan chain is folded into multiple segments that receive inputs in parallel.

4. The method of claim 1 , further comprising:

providing a second scan chain of flip-flops operative to receive scan input data in parallel with the first scan chain.

5. The method of claim 4 , wherein, when the first scan chain is operated in the rotate mode, at least some of the flip-flops of the first and second scan chain that occupy corresponding data positions contain different data.

6. The method of claim 1 , wherein the scan chains form part of an integrated circuit; and further comprising:

analyzing data adjacencies of scan chains of the integrated circuit.

7. The method of claim 6 , further comprising:

applying test patterns to the integrated circuit based, at least in part, upon the data adjacencies.

8. A method for reconfiguring scan chains comprising:

providing an integrated circuit having a first scan chain and a second scan chain operative in parallel such that flip-flops of the first scan chain and the second scan chain that occupy corresponding data positions contain identical scan input data; and

selectively reconfiguring the second scan chain such that flip-flops of the first scan chain and the second scan chain that occupy corresponding data positions do not contain identical scan input data.

9. The method of claim 8 , wherein, in selectively reconfiguring the second scan chain, a last of the flip-flops of the second scan chain receives scan input data prior to a first of the flip-flops of the second scan chain such that last of the flip-flops of the second scan chain receives scan input data identical to scan input data received by a first of the flip-flops of the first scan chain.

10. A system for reconfiguring a scan chain, comprising:

a first scan chain of flip-flops operative in either a normal mode or a rotate mode such that, if the first scan chain is operative in the normal mode, inputs are provided to the flip-flops in sequential order with a first of the flip-flops receiving an input prior to a second of the flip-flops, and, if the first scan chain is operative in the rotate mode, inputs are provided to the flip-flops with the first of the flip-flops receiving an input subsequent to the second of the flip-flops.

11. The system of claim 10 , further comprising:

means for determining whether the first scan chain is to be operated in either the normal mode or the rotate mode.

12. The system of claim 10 , further comprising:

an integrated circuit, wherein the first scan chain is a portion of the integrated circuit.

Assignments (9)