Method and apparatus of reducing scan power in the process of unloading and restoring processor content by scan chain partition and disable
A method and an apparatus are provided for reducing scan power consumption when unloading and restoring content of a processor. The processor has one or more scan chains. First, at least one scan chain is partitioned into a plurality of segments. Second, one of the segments is scanned at a time.
1 . A method for reducing scan power consumption when unloading and restoring content of a processor having one or more scan chains, the method comprising the steps of:
partitioning at least one scan chain into a plurality of segments; and
scanning one of the plurality of segments at a time.
2 . The method of claim 1 , wherein the plurality of segments comprises one or more segments of a predetermined length and an offset segment.
3 . The method of claim 2 , wherein the offset segment is used to handle variations in length between the one or more scan chains.
4 . The method of claim 1 , wherein the step of scanning one of the plurality of segments at a time comprises the steps of:
providing enough clocking to scan all bits in the one of the plurality of segments; and
keeping track of the predetermined length, an order of the segments, and the offset segment.
5 . The method of claim 1 , further comprising the step of scanning any remaining one or more of the plurality of segments one at a time to complete scanning the at least one scan chain.
6 . The method of claim 1 , further comprising the steps of:
partitioning any remaining one or more of the one or more scan chains into a plurality of segments; and
scanning the plurality of segments one at a time.
7 . An apparatus for reducing scan power consumption when unloading and restoring content of a processor having one or more scan chains, the apparatus comprising:
means for partitioning at least one scan chain into a plurality of segments; and
means for scanning one of the plurality of segments at a time.
8 . The apparatus of claim 7 , wherein the plurality of segments comprises one or more segments of a predetermined length and an offset segment.
9 . The apparatus of claim 8 , wherein the offset segment is used to handle variations in length between the one or more scan chains.
10 . The apparatus of claim 7 , wherein the means for scanning one of the plurality of segments at a time comprises:
means for providing enough clocking to scan all bits in the one of the plurality of segments; and
means for keeping track of the predetermined length, an order of the segments, and the offset segment.
11 . The apparatus of claim 7 , further comprising means for scanning any remaining one or more of the plurality of segments one at a time to complete scanning the at least one scan chain.
12 . The apparatus of claim 7 , further comprising:
partitioning any remaining one or more of the one or more scan chains into a plurality of segments; and
scanning the plurality of segments one at a time.
13 . A computer program product for reducing scan power consumption when unloading and restoring content of a processor having one or more scan chains, the computer program product having a medium with a computer program embodied thereon, the computer program comprising:
computer program code for partitioning at least one scan chain into a plurality of segments; and
computer program code for scanning one of the plurality of segments at a time.
14 . The computer program product of claim 13 , wherein the plurality of segments comprises one or more segments of a predetermined length and an offset segment.
15 . The computer program product of claim 14 , wherein the offset segment is used to handle variations in length between the one or more scan chains.
16 . The computer program product of claim 13 , wherein the computer program code for scanning one of the plurality of segments at a time comprises:
computer program code for providing enough clocking to scan all bits in the one of the plurality of segments; and
computer program code for keeping track of the predetermined length, an order of the segments, and the offset segment.
17 . The computer program product of claim 13 , the computer program further comprising computer program code for scanning any remaining one or more of the plurality of segments one at a time to complete scanning the at least one scan chain.
18 . The computer program product of claim 13 , the computer program further comprising:
computer program code for partitioning any remaining one or more of the one or more scan chains into a plurality of segments; and
computer program code for scanning the plurality of segments one at a time.
19 . Scan circuitry for reducing scan power consumption when unloading and restoring content of a processor having one or more scan chains, the scan circuitry comprising:
a scan structure comprising one or more scan chains, wherein at least one of the one or more scan chain is partitioned into a plurality of segments; and
a master controller coupled to the scan structure for scanning one of the plurality of segments at a time.
20 . The scan circuitry of claim 19 , further comprising an off-chip memory coupled to the master controller for storing unloaded content of the processor.