Patent Application
20240175921
This non-provisional application claims priority under 35 U.S.C. § 119(a) to Patent Application No. 111146042 filed in Taiwan, R.O.C. on Nov. 30, 2022, the entire contents of which are hereby incorporated by reference.
The instant disclosure is related to circuit testing, especially a chip having a clock masking circuit which has the functions of reducing area costs of the circuits under test and increasing test coverage.
In transition delay fault (TDF) tests known to the inventor, on-chip clock controllers (OCCs) are used to apply full-speed clock pulses to test whether the devices under test (DUTs) are able to operate at their target operation frequencies. However, some circuits internal to the DUTs may operate at slower clock frequencies, or the clock frequencies of some circuits internal to the DUTs may be preconfigured and be constant values during the operation of the DUTs. For these circuits, timing constraint is usually used to avoid circuit synthesis tools or automatic placement and routing (APR) tools spending too much effort on these circuits.
However, circuits constrained by timing cannot timely generate correct outputs; instead, these circuits will generate unknown signals. These unknown signals will affect test results. The level of effect of the unknown signals is proportional to the number of time constraints or the range of time constraint coverage. Conventionally, commercial tools mask the effect of unknown signals by locating all terminals of the scan flip-flops affected by the unknown signals and adding gating circuits at the terminals of each affected scan flip-flop.
However, adding the gating circuits to mask the effect of the unknown signals leads to additional area costs of the DUTs, and the gating circuits may also mask test responses transmitted by the DUTs through the actual functional paths and thus further cause the test coverage to decrease.
In an embodiment, a chip comprises a first circuit under test, a second circuit under test, and a clock masking circuit. The second circuit under test is coupled to the first circuit under test. The clock masking circuit comprises a first clock control circuit, a second clock control circuit, and an enabling circuit. The first clock control circuit is configured to provide a first clock signal for the first circuit under test according to a first enable signal and an initial clock signal. The second clock control circuit is configured to provide a second clock signal for the second circuit under test according to a second enable signal and the initial clock signal. The enabling circuit is configured to provide the first enable signal for the first clock control circuit and provide the second enable signal for the second clock control circuit. During a first operation period, the first enable signal enables the first clock control circuit to provide the first clock signal for the first circuit under test, and the second enable signal disables the second clock control circuit from providing the second clock signal for the second circuit under test. During a second operation period, the first enable signal disables the first clock control circuit from providing the first clock signal for the first circuit under test, and the second enable signal enables the second clock control circuit to provide the second clock signal for the second circuit under test. The first operation period does not overlap with the second operation period.
In an embodiment, a chip comprises a first circuit under test, a second circuit under test, and a clock masking circuit. The second circuit under test is coupled to the first circuit under test. The clock masking circuit comprises a first clock control circuit, a second clock control circuit, and an enabling circuit. The first clock control circuit is configured to provide a first clock signal for the first circuit under test according to a first enable signal and an initial clock signal. The second clock control circuit is configured to provide a second clock signal for the second circuit under test according to a second enable signal and the initial clock signal. The enabling circuit is configured to provide the first enable signal for the first clock control circuit and provide the second enable signal for the second clock control circuit. During a first operation period, the first enable signal enables the first clock control circuit to provide the first clock signal for the first circuit under test, and the second enable signal disables the second clock control circuit from providing the second clock signal for the second circuit under test. During a second operation period, the first enable signal disables the first clock control circuit from providing the first clock signal for the first circuit under test, and the second enable signal enables the second clock control circuit to provide the second clock signal for the second circuit under test. During a third operation period, the first enable signal enables the first clock control circuit to provide the first clock signal for the first circuit under test, and the second enable signal enables the second clock control circuit to provide the second clock signal for the second circuit under test. The first operation period, the second operation period, and the third operation period do not overlap with each other.
In an embodiment, a chip comprises a first circuit under test, a second circuit under test, a clock source circuit, and a clock masking circuit. The second circuit under test is coupled to an input end of the first circuit under test. The clock source circuit is configured to provide an initial clock signal. The clock masking circuit comprises a first clock control circuit and an enabling circuit. The first clock control circuit is configured to provide a first clock signal for the first circuit under test according to a first enable signal and the initial clock signal. The enabling circuit is configured to provide the first enable signal for the first clock control circuit. During a first operation period, the first enable signal enables the first clock control circuit to provide the first clock signal for the first circuit under test, and the clock source circuit provides the initial clock signal for the second circuit under test. During a second operation period, the first enable signal disables the first clock control circuit from providing the first clock signal for the first circuit under test, and the clock source circuit provides the initial clock signal for the second circuit under test. The first operation period does not overlap with the second operation period.
In an embodiment, a chip comprises a first circuit under test, a third circuit under test, a clock source circuit, and a clock masking circuit. The third circuit under test is coupled to an output end of the first circuit under test. The clock source circuit is configured to provide an initial clock signal. The clock masking circuit comprises a first clock control circuit and an enabling circuit. The first clock control circuit is configured to provide a first clock signal for the first circuit under test according to a first enable signal and the initial clock signal. The enabling circuit is configured to provide the first enable signal for the first clock control circuit. During a first operation period, the first enable signal enables the first clock control circuit to provide the first clock signal for the first circuit under test, and the clock source circuit provides the initial clock signal for the third circuit under test. During a second operation period, the first enable signal disables the first clock control circuit from providing the first clock signal for the first circuit under test, and the clock source circuit provides the initial clock signal for the third circuit under test. The first operation period does not overlap with the second operation period.
The following will describe the detailed features and advantages of the instant disclosure in detail in the detailed description. The content of the description is sufficient for any person skilled in the art to comprehend the technical context of the instant disclosure and to implement it accordingly. According to the content, claims and drawings disclosed in the instant specification, any person skilled in the art can readily understand the goals and advantages of the instant disclosure.
The instant disclosure will become more fully understood from the detailed
description given herein below for illustration only, and thus not limitative of the instant disclosure, wherein:
The first circuit under test 10 and the second circuit under test 20 are circuits that are under test in a transition delay fault (TDF) test. In some embodiments, a time domain of the first circuit under test 10 and a time domain of the second circuit under test 20 are different time domains, and the first circuit under test 10 and the second circuit under test 20 may be, but not limited to, implemented using one or more scan flip-flops.
In some embodiments, the TDF test for the chip 1 includes a shift phase and a capture phase. During the shift phase, the scan flip-flop internal to the first circuit under test 10 and the scan flip-flop internal to the second circuit under test 20 receive test patterns by scanning input signals and slowly shifting clocks. During the capture phase, the first circuit under test 10 and the second circuit under test 20 obtain test responses according to the test patterns received during the shift phase and compare the test responses with a default correct value to obtain test results. In some embodiments, the TDF test for the chip 1 changes between the shift phase and the capture phase according to a scan enable signal.
In some embodiments, the connection circuit 30 may be implemented using one or more hardware modules. In different embodiments, the hardware modules may be logic gates, adders, multipliers, latches, registers, or flip-flops, and the types of hardware modules are not limited in the instant disclosure.
In some embodiments, a timing constraint causes a data path from the first circuit under test 10 to the second circuit under test 20 and the data path from the second circuit under test 20 to the first circuit under test 10 to both be false paths or multicycle paths. In some embodiments, commands for the timing constraint may be, but not limited to, set_false_path, set_clock_group, or set_multicycl_path.
The clock masking circuit 40 comprises a first clock control circuit 41, a second clock control circuit 42, and an enabling circuit 43. The first clock control circuit 41 is configured to provide a first clock signal CLK1 for the first circuit under test 10 according to a first enable signal EN1 and an initial clock signal CLK. The second clock control circuit 42 is configured to provide a second clock signal CLK2 for the second circuit under test 20 according to a second enable signal EN2 and the initial clock signal CLK. The enabling circuit 43 is configured to provide the first enable signal EN1 for the first clock control circuit 41 and provide the second enable signal EN2 for the second clock control circuit 42. In some embodiments, the enabling circuit 43 comprises a first enabling unit 44 and an inverter 45. The first enabling unit 44 is configured to provide the first enable signal ENI for the first clock control circuit 41. The inverter 45 is configured to invert the first enable signal EN1 so as to provide the second enable signal EN2 for the second clock control circuit 42. In some embodiments, the inverter 45 may be, but not limited to, a PMOS inverter, an NMOS inverter, or a CMOS inverter.
As a result, during the first operation period T1, because the second clock signal CLK2 is inhibited, data of the second circuit under test 20 will not be captured by the first circuit under test 10, and the scan flip-flop which is internal to the first circuit under test 10 and uses the time domain of the first clock signal CLK1 can still capture the test responses. On the contrary, during the second operation period T2, because the first clock signal CLK1 is inhibited, data of the first circuit under test 10 will not be captured by the second circuit under test 20, and the scan flip-flop which is internal to the second circuit under test 20 and uses the time domain of the second clock signal CLK2 can still capture the test responses. As a result, the clock masking circuit 40 allows the chip 1 to only activate one time domain during a single capture phase to prevent the second circuit under test 20 from capturing the data of the first circuit under test 10 from the first circuit under test 10 or prevent the first circuit under test 10 from capturing the data of the second circuit under test 20 from the second circuit under test 20. Therefore, the propagation of the unknown signals of the first circuit under test 10 and the second circuit under test 20 can be thus avoided without affecting the abilities of the first circuit under test 10 and the second circuit under test 20 to capture the test responses, so that the test coverage of the chip 1 is increased. As a result, design for gating circuits for masking unknown signals is not necessarily required, and the area cost internal to the chip 1 is reduced.
In some embodiments, each of the first clock control circuit 41 and the second clock control circuit 42 is a latch. Each of the first clock control circuit 41 and the second clock control circuit 42 comprises an enabling end EN, an output end Q, a scan enabling end SE, and a clock end CK. The enabling end EN of the first clock control circuit 41 is configured to receive the first enable signal EN1 provided by the first enabling circuit 44. The enabling end EN of the second clock control circuit 42 is configured to receive the second enable signal EN2 provided by the inverter 45. The output end Q of the first clock control circuit 41 is configured to provide the first clock signal CLK1 for the first circuit under test 10. The output end Q of the second clock control circuit 42 is configured to provide the second clock signal CLK2 for the second circuit under test 20. The scan enabling end SE of the first clock control circuit 41 and the scan enabling end SE of the second clock control circuit 42 are configured to receive the scan enable signal scan_en. The clock end CK of the first clock control circuit 41 and the clock end CK of the second clock control circuit 42 are configured to receive the initial clock signal CLK and the shift clock signal SHIFT_CLK provided by the clock source circuit 50.
When the test changes from the shift phase S1 to the first operation period T1, the output end Q of the first enabling unit 44 will be loaded to 1 and will be maintained at 1 throughout the first operation period T1. In other words, in some embodiments, the first enable signal EN1 is maintained at 1 during the first operation period T1. During the first operation period T1, because the enabling end EN of the first clock control circuit 41 receives the first enable signal EN1 which is provided by the first enabling unit 44 and has the signal value of 1, the first clock control circuit 41 takes the initial clock signal CLK received by the clock end CK of the first clock control circuit 41 as the first clock signal CLK1 and provides the first clock signal CLK1 for the first circuit under test 10.
The second enable signal EN2 is a signal obtained by sending the first enable signal EN1 through the inverter 45, and the first enable signal EN1 is maintained at 1 during the first operation period T1. As a result, the second enable signal EN2 is maintained at 0 during the first operation period T1. During the first operation period T1, because the enabling end EN of the second clock control circuit 42 receives the second enable signal EN2 which is provided by the inverter 45 and has the signal value of 0, the second clock control circuit 42 does not take the initial clock signal CLK received by the clock end CK of the second clock control circuit 42 as the second clock signal CLK2 and does not provide the second clock signal CLK2 for the second circuit under test 20. In other words, in some embodiments, the second circuit under test 20 will not receive any clock signal during the first operation period T1.
When the test changes from the shift phase S3 to the second operation period T2, the output end Q of the first enabling unit 44 will be loaded to 0 and will be maintained at 0 throughout the second operation period T2. In other words, in some embodiments, the first enable signal EN1 is maintained at 0 during the second operation period T2. During the second operation period T2, because the enabling end EN of the first clock control circuit 41 receives the first enable signal EN1 which is provided by the first enabling unit 44 and has the signal value of 0, the first clock control circuit 41 does not take the initial clock signal CLK received by the clock end CK of the first clock control circuit 41 as the first clock signal CLK1 and does not provide the first clock signal CLK1 for the first circuit under test 10. In other words, in some embodiments, the first circuit under test 10 will not receive any clock signal during the second operation period T2.
The second enable signal EN2 is a signal obtained by sending the first enable signal EN1 through the inverter 45, and the first enable signal EN1 is maintained at 0 during the second operation period T2. As a result, the second enable signal EN2 is maintained at 1 during the second operation period T2. During the second operation period T2, because the enabling end EN of the second clock control circuit 42 receives the second enable signal EN2 which is provided by the inverter 45 and has the signal value of 1, the second clock control circuit 42 takes the initial clock signal CLK received by the clock end CK of the second clock control circuit 42 as the second clock signal CLK2 and provides the second clock signal CLK2 for the second circuit under test 20.
The clock source circuit 50 is configured to provide the shift clock signal SHIFT_CLK and the initial clock signal CLK for the clock masking circuit 40. In some embodiments, the clock source circuit 50 may be, but not limited to, an on-chip clock controller (OCC).
In some embodiments, the timing constraint causes the data path from the first circuit under test 10 to the second circuit under test 20 to be a false path or a multicycle path but causes the data path from the second circuit under test 20 to the first circuit under test 10 to be a true path.
In some embodiments, the first enable signal EN1 is maintained at 1 during the first operation period T1. During the first operation period T1, because the enabling end EN of the first clock control circuit 41 receives the first enable signal EN1 which is provided by the first enabling unit 44 and has the signal value of 1, the first clock control circuit 41 takes the initial clock signal CLK received by the clock end CK of the first clock control circuit 41 as the first clock signal CLK1 and provides the first clock signal CLK1 for the first circuit under test 10. The second enable signal EN2 is maintained at 0 during the first operation period T1. During the first operation period T1, because the enabling end EN of the second clock control circuit 42 receives the second enable signal EN2 which is provided by the second enabling unit 46 and has the signal value of 0, the second clock control circuit 42 does not take the initial clock signal CLK received by the clock end CK of the second clock control circuit 42 as the second clock signal CLK2 and does not provide the second clock signal CLK2 for the second circuit under test 20. In other words, in some embodiments, the second circuit under test 20 will not receive any clock signal during the first operation period T1.
In some embodiments, the first enable signal EN1 is maintained at 0 during the second operation period T2. During the second operation period T2, because the enabling end EN of the first clock control circuit 41 receives the first enable signal EN1 which is provided by the first enabling unit 44 and has the signal value of 0, the first clock control circuit 41 does not take the initial clock signal CLK received by the clock end CK of the first clock control circuit 41 as the first clock signal CLK1 and does not provide the first clock signal CLK1 for the first circuit under test 10. In other words, in some embodiments, the first circuit under test 10 will not receive any clock signal during the second operation period T2. The second enable signal EN2 is maintained at 1 during the second operation period T2. During the second operation period T2, because the enabling end EN of the second clock control circuit 42 receives the second enable signal EN2 which is provided by the second enabling unit 46 and has the signal value of 1, the second clock control circuit 42 takes the initial clock signal CLK received by the clock end CK of the second clock control circuit 42 as the second clock signal CLK2 and provides the second clock signal CLK2 for the second circuit under test 20.
In some embodiments, the first enable signal EN1 is maintained at 1 during the third operation period T3. During the third operation period T3, because the enabling end EN of the first clock control circuit 41 receives the first enable signal EN1 which is provided by the first enabling unit 44 and has the signal value of 1, the first clock control circuit 41 takes the initial clock signal CLK received by the clock end CK of the first clock control circuit 41 as the first clock signal CLK1 and provides the first clock signal CLK1 for the first circuit under test 10. The second enable signal EN2 is also maintained at 1 during the third operation period T3. During the third operation period T3, because the enabling end EN of the second clock control circuit 42 receives the second enable signal EN2 which is provided by the second enabling unit 46 and has the signal value of 1, the second clock control circuit 42 takes the initial clock signal CLK received by the clock end CK of the second clock control circuit 42 as the second clock signal CLK2 and provides the second clock signal CLK2 for the second circuit under test 20.
In some embodiments, the time domain of the first circuit under test 10 and the time domain of the second circuit under test 20 are the same time domain, and the timing constraint causes the data path from the first circuit under test 10 to the second circuit under test 20 and the data path from the second circuit under test 20 to the first circuit under test 10 to both be multicycle paths.
The clock masking circuit 40 comprises the first clock control circuit 41 and an enabling circuit 43. The first clock control circuit 41 is configured to provide the first clock signal CLK1 for the first circuit under test 10 according to the first enable signal EN1 and the initial clock signal CLK. The enabling circuit 43 is configured to provide the first enable signal EN1 for the first clock control circuit 41. The enabling circuit 43 is configured to provide the first enable signal ENI for the first clock control circuit 41. The enabling circuit 43 comprises the first enabling unit 44 and the inverter 45. The first enabling unit 44 is configured to provide the first enable signal EN1 for the first clock control circuit 41. The inverter is coupled to the output end of the first enabling unit 44 and the input end of the first enabling unit 44.
In some embodiments, the chip 1 further comprises a third circuit under test 60. The third circuit under test 60 is coupled to the output end of the first circuit under test 10. During the first operation period T1 and the second operation period T2, the clock source circuit 50 further provides the initial clock signal CLK for the third circuit under test 60.
The clock masking circuit 40 comprises a first clock control circuit 41 and an enabling circuit 43. The first clock control circuit 41 is configured to provide the first clock signal CLK1 for the first circuit under test 10 according to the first enable signal EN1 and the initial clock signal CLK. The enabling circuit 43 is configured to provide the first enable signal EN1 for the first clock control circuit 41. The enabling circuit 43 comprises the first enabling unit 44 and the inverter 45. The first enabling unit 44 is configured to provide the first enable signal EN1 for the first clock control circuit 41. The inverter 45 is coupled to the output end of the first enabling unit 44 and the input end of the first enabling unit 44.
During the first operation period T1, the first enable signal EN1 enables the first clock control circuit 41 to provide the first clock signal CLK1 for the first circuit under test 10, and the clock source circuit 50 provides the initial clock signal CLK for the third circuit under test 60. During a second operation period T2, the first enable signal EN1 disables the first clock control circuit 41 from providing the first clock signal CLK1 for the first circuit under test 10, and the clock source circuit 50 provides the initial clock signal CLK for the third circuit under test 60. The first operation period T1 does not overlap with the second operation period T2.
As above, in some embodiments, the clock masking circuit 40 can prevent the second circuit under test 20 from capturing the data of the first circuit under test 10 from the first circuit under test 10 or prevent the first circuit under test 10 from capturing the data of the second circuit under test 20 from the second circuit under test 20 during the capture phase. Therefore, the propagation of the unknown signals of the first circuit under test 10 and the second circuit under test 20 can be thus avoided without affecting the abilities of the first circuit under test 10 and the second circuit under test 20 to capture the test responses, so that the test coverage of the chip 1 is increased. Design for gating circuits for masking unknown signals is not necessarily required, and the area cost internal to the chip 1 is reduced.
Although the technical context of the instant disclosure has been disclosed with the preferred embodiments above, the embodiments are not meant to limit the instant disclosure. Any adjustment and retouch done by any person skill in the art without deviating from the spirit of the instant disclosure shall be covered by the scope of the instant disclosure. Therefore, the protected scope of the instant disclosure shall be defined by the attached claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 111146042 | Nov 2022 | TW | national |
