Reconfigurable scan chain connectivity to enable flexible device I/O utilization

1. A device under test (DUT) comprising:

a plurality of scan chains;

a plurality of shift register elements, each associated with a respective one of the scan chains; and

a programmable switch matrix to configure shift register elements of a subset of the plurality of shift register elements to cause one shift register element of the subset to receive an interleaved test sequence, and to cause the interleaved test sequence to be shifted to other shift register elements in the subset and to input deinterleaved test sequences to scan chains associated with the subset.

2. The DUT of claim 1 , further comprising a plurality of device scan pins each associated with a shift register element.

3. The DUT of claim 2 , wherein the device scan pin associated with the one shift register element provides the interleaved test sequence to the subset.

4. The DUT of claim 3 , wherein the programmable switch matrix configures multiplexers in each of the shift register elements of the subset such that

the one shift register element uses a parallel path to receive the interleaved test sequence from the device scan pin associated with the one shift register element; and

the other shift register elements in the subset use a serial path to receive the interleaved test sequences from the one shift register element.

5. The DUT of claim 4 , wherein the programmable switch matrix further comprises at least one configurable crossbar switch for routing the interleaved test sequence from any of the device scan pins to any of the plurality of shift register elements.

6. The DUT of claim 5 , wherein the at least one configurable crossbar switch is configured to balance the number of shift events between a plurality of subsets.

7. The DUT of claim 3 , further comprising a bypass path for bypassing the plurality of shift register elements.

8. The DUT of claim 1 , further comprising

a second programmable switch matrix to configure a subset of shift register elements at the output of the scan chains to cause the shift register elements of the subset at the output to receive deinterleaved test sequences to be shifted to one of the shift register elements in the subset at the output, such that an interleaved output test sequence is provided to an output pin associated with the one of the shift register elements in the subset at the output.

9. The DUT of claim 8 , wherein the programmable switch matrix configures multiplexers in each of the shift register elements of the subset at the output such that

the one of the shift register elements in the subset at the output uses a parallel path to provide the interleaved output test sequence to the output pin; and,

the register elements in the subset at the output use a serial path to provide the deinterleaved test sequences to the one of the shift register elements in the subset at the output.

10. The DUT of claim 9 , wherein the programmable switch matrix further comprises at least a second crossbar switch for routing interleaved test sequences from any shift register elements at the output to any output pin.

11. The DUT of claim 10 , wherein the at least a second crossbar switch is configured to balance the number of shift events between a plurality of subsets of shift register elements at the output of the scan chains.

12. The DUT of claim 9 , further comprising a bypass path for bypassing the shift register elements at the output of the scan chains.

13. A method of testing a device under test (DUT), the DUT having a plurality of scan chains and a plurality of shift register elements each associated with a respective scan chain, the method comprising:

determining a subset of the plurality of shift register elements to receive an interleaved test sequence;

programmably configuring one shift register element of the subset to receive the interleaved test sequence;

receiving the interleaved test sequence at the one shift register element;

programmably configuring the other shift registers in the subset to shift the interleaved test sequence to others in the subset and to input deinterleaved test sequences to scan chains associated with the subset; and,

receiving deinterleaved test sequences output from the scan chains.

14. The method of claim 13 , wherein programmably configuring includes programmably re-configuring.

15. A device under test (DUT) comprising:

a plurality of scan chains;

a plurality of shift register elements, each associated with a respective one of the scan chains; and

a programmable switch matrix to configure a subset of shift register elements at the output of the scan chains to cause the shift register elements of the subset at the output to receive deinterleaved test sequences to be shifted to one of the shift register elements in the subset at the output and to provide an interleaved output test sequence to an output pin associated with the one of the shift register elements in the subset at the output.

16. The DUT of claim 15 , wherein the programmable switch matrix configures multiplexers in each of the shift register elements of the subset at the output such that

the one of the shift register elements in the subset at the output uses a parallel path to provide the interleaved output test sequence to the output pin; and,

the register elements in the subset at the output use a serial path to provide the deinterleaved test sequences to the one of the shift register elements in the subset at the output.

17. The DUT of claim 16 , wherein the programmable switch matrix further comprises a at least one configurable crossbar switch for routing the interleaved output test sequence from any of the shift register elements to any of a plurality of output pins.

18. The DUT of claim 17 , wherein the at least one configurable crossbar switch is configured to balance the number of shift events between a plurality of subsets.

19. The DUT of claim 18 , further comprising a bypass path for bypassing the plurality of shift register elements.