US 7,627,798 B2Granted

Systems and methods for circuit testing using LBIST

AssigneeKabushiki Kaisha Toshiba

InventorNaoki Kiryu

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Abstract

Systems and methods for performing logic built-in-self-tests (LBISTS) in digital circuits. In one embodiment, the operation of LBIST circuitry is suspended at the end of each test cycle so that the bit patterns generated by the functional logic of the device under test can be examined to determine if any errors occurred during the test cycle. Pseudorandom bit patterns are scanned into the scan chains interposed between portions of the functional logic circuit and then propagated through the functional logic. The resulting bit patterns are captured in scan chains following the functional logic and then scanned out of the scan chains. The bit patterns are processed and compared to corresponding data generated by a parallel LBIST system in a device that is known to operate properly. The LBIST test cycles are then halted if there are errors in the generated bit patterns or resumed if there are no errors.

Claims13

Dependent claims

A method for performing a series of test cycles using pseudorandom patterns of bits in a logic built-in self test (LBIST) system, wherein the LBIST system includes a plurality of scan chains and a pseudorandom pattern generator (PRPG), wherein the plurality of scan chains extend between portions of functional logic of a device under test and are connected to each other through the portions of functional logic, each of the scan chains including a plurality of scan latches disposed correspondingly to levels of functional logic, and wherein the PRPG is coupled to the plurality of scan chains and configured to generate pseudorandom patterns of bits to be scanned into the scan chains, the method comprising, in each of the test cycles:

executing a functional phase in which functional operations are performed, including propagating data through the portions of functional logic of the device under test;
executing a first hold phase following the functional phase, wherein in the first hold phase functional operations are suspended and data propagated through the portions of functional logic of the device under test is held;
executing a scan shift phase in which scan shift operations are performed, including scanning data into and out of the scan latches through the plurality of the scan chains;
and
executing a second hold phase following the scan shift phase in which functional operations and scan shift operations are suspended, data scanned out of the plurality of scanned chains is analyzed, and a determination is made, based on the analyzed data scanned out of the plurality of scanned chains, whether to resume functional operations and scan shift operations for a subsequent test cycle, wherein, when the determination is to resume functional operations and scan shift operations for the subsequent test cycle, functional operations and scan shift operations for the subsequent test cycle are resumed without re-initializing the LBIST system.

2 more elements

A logic built-in self test (LBIST) system comprising:

a plurality of scan chains extending between portions of functional logic of a device under test, and connected to each other through the portions of functional logic, each of the scan chains including a plurality of scan latches disposed correspondingly to levels of functional logic;
and
a pseudorandom pattern generator (PRPG) coupled to the plurality of scan chains and configured to generate pseudorandom patterns of bits to be scanned into the scan chains;
and
an LBIST controller configured to generate control signals to control the LBIST system to perform test cycles respectively using the pseudorandom patterns of bits, wherein the LBIST controller is configured to cause the LBIST system to execute, in each of the test cycles:
a functional phase in which functional operations are performed, including propagating data through the portions of functional logic of the device under test,
a first hold phase following the functional phase, wherein in the first hold phase functional operations are suspended and data propagated through the portions of functional logic of the device under test is held,
a scan shift phase in which scan shift operations are performed, including scanning data into and out of the scan latches through the plurality of the scan chains, and
a second hold phase following the scan shift phase in which functional operations and scan shift operations are suspended, including analyzing data scanned out of the plurality of scanned chains, and making a determination, based on the analyzing of the data scanned out of the plurality of scanned chains, whether to resume functional operations and scan shift operations for a subsequent test cycle, wherein, when the determination is to resume functional operations and scan shift operations for the subsequent test cycle, functional operations and scan shift operations for the subsequent test cycle are resumed, without re-initializing the LBIST system.

6 more elements

A system comprising:

a first device having LBIST circuitry incorporated therein, wherein the first device is a device under test;
a second device having LBIST circuitry incorporated therein, wherein the second device is known to operate without errors;
one or more LBIST controllers coupled to the first and second devices and configured to control each of the first and second devices to execute one or more LBIST test cycles, wherein each of the test cycles includes
a functional phase in which functional operations are performed, including propagating data through functional logic of the device under test,
a scan shift phase in which scan shift operations are performed, including scanning data into and out of a plurality of scan chains interposed between portions of the functional logic of the device under test, and
a hold phase in which functional operations and scan shift operations are suspended,
during the hold phase of each test cycle, compare data scanned out of the scan chains of the first device to data scanned out of the scan chains of the second device, and
resume functional operations and scan shift operations for a subsequent test cycle without re-initializing the LBIST circuitry of the first and second devices when the data scanned out of the scan chains of the first device are the same as the data scanned out of the scan chains of the second device.

5 more elements

Dependencies are inferred from the claim text.