A detection circuit, a detection card and a detection method

Abstract

The present application relates to the field of electric fault detection, in particular to a detection circuit, a detection card and a detection method, the detection circuit comprising a connection module, a pull-up module and a pull-down module, further comprising a first voltage division module connected with the connection module and the pull-up module, sharing the voltage in the circuit when the circuit is short-circuited or open-circuited; a first control module connected with the first voltage division module, controlling the conduction of the first voltage division module with the connection module and the pull-up module; a second voltage division module connected with the connection module and the pull-down module, sharing the voltage in the circuit when the circuit is short-circuited or open-circuited; and a second control module connected with the second voltage division module, controlling the conduction of the second voltage division module with the connection module and the pull-down module. The present application has the effect of reliably detecting the short-circuit and open-circuit of the pull-up and pull-down of the DUT, and improving the safety in the detection process.

Description

Technical Field

[0001] This invention relates to the field of electrical fault detection, and in particular to a detection circuit, a detection card, and a detection method. Background Technology

[0002] In the field of boundary scan test (BST) fixtures, the DUMMY card is a test card fixed on an automated fixture. It continuously interfaces with the BST board to achieve automated testing of the board. In the field of boundary scan, it is necessary to achieve comprehensive testing coverage of all connections of the board under test. Although some connections have been tested according to existing methods, reliability analysis of the methods revealed that the conventional testing method has defects in testing pull-up and pull-down open short circuits of a certain board under test. Therefore, it is necessary to consider the reliability of the testing method itself and find a more reliable testing method that can fully cover the testing of pull-up and pull-down open short circuit connections. In existing methods, the connection between the boundary scan test board (DUT) and the boundary scan DUMMY test card (DUMMY card) is fixed. By analyzing the fixed connection, a fixed expected level is generated to perform boundary scan testing on the DUT. This testing method has its limitations. When some I / Os of the boundary scan chip of the DUT have pull-up or pull-down, and the I / Os are led to the connector under test, the existing method cannot reliably and safely perform boundary scan testing on such I / Os with pull-up or pull-down short circuits.

[0003] There are two existing testing methods. One method is to consider the I / O of the DUT and the DUMMY card, with one end as the output to send high and low levels, and the other end as the input to receive high and low levels.

[0004] For example, when the pull-up is normal, the boundary scan chip IO inside the DUT outputs 1, and the IO of the DUMMY card will receive 1 accordingly; when the boundary scan chip IO inside the DUT outputs 0, the IO of the DUMMY card will receive 0 accordingly.

[0005] When the pull-up switch is open, the test results are the same as when it is normal. Therefore, this method of transmitting and receiving cannot test whether the pull-up switch of the DUT is open.

[0006] When pulled up and short-circuited, the boundary scan chip IO inside the DUT outputs 1, and the DUMMY card IO will receive 1 accordingly. When the boundary scan chip IO inside the DUT outputs 0, the DUMMY card IO receives an unknown value. In addition, when the boundary scan chip IO inside the DUT outputs 0, it is equivalent to a short circuit between the power supply inside the DUT and the chip itself. The power supply inside the DUT has a strong driving capability and is not easily pulled low. Therefore, a large current will be injected into the boundary scan chip in an instant, which may burn out the boundary scan chip inside the DUT.

[0007] Similarly, if the transmit / receive relationship between the DUT and the DUMMY card is reversed, that is, the boundary scan chip IO outputs 0 in the DUMMY card and the IO of the connected DUT receives it, there is a risk of burning out the boundary scan chip in the DUMMY card when the pull-up is short-circuited.

[0008] Another method is input detection. For example, when testing the pull-up pin of the DUT (Device Under Test), the DUT and the DUMMY card's I / O are connected. Input detection can be performed if input detection is supported. When the pull-up pin is normal, the detected level is 1. When the pull-up pin is open, due to the floating I / O pin, the detected level may be stable at 1, stable at 0, or fluctuate between 0 and 1. Therefore, the probability of false positives for open pull-up pins is high. When the pull-up pin is short-circuited, the detected level is 1, consistent with the normal situation. Therefore, the input detection method cannot test for short-circuited pull-ups.

[0009] Since the testing method for dropdowns is the same as that for pullup controls, it will not be repeated here. Similarly, when performing boundary scan testing on dropdowns, the same issues as with pullup controls also exist.

[0010] In summary, among the existing methods, boundary scan tests considering pull-up and pull-down are not highly reliable when the circuit is open; and there are certain security risks in transmit / receive tests when the circuit is short-circuited. Summary of the Invention

[0011] In order to reliably detect short circuits and open circuits in the pull-up and pull-down terminals of the DUT and improve the safety of the detection process, this invention provides a detection circuit, a detection card, and a detection method.

[0012] This invention provides a detection circuit, which adopts the following technical solution:

[0013] A detection circuit includes a connection module, a pull-up module, and a pull-down module, and further includes a first voltage divider module connected to the connection module and the pull-up module, which distributes the voltage in the circuit when the circuit is short-circuited or open-circuited;

[0014] A first control module is connected to the first voltage divider module and controls the conduction between the first voltage divider module and the connection module and the pull-up module.

[0015] The second voltage divider module is connected to the connection module and the pull-down module, and distributes the voltage in the circuit when the circuit is short-circuited or open-circuited.

[0016] The second control module is connected to the second voltage divider module and controls the conduction between the second voltage divider module and the connection module and the pull-down module.

[0017] In one specific implementation scheme, both the first control module and the second control module are switch groups.

[0018] In one specific implementation, the first voltage divider module includes a first resistor group and a second resistor group, and the second voltage divider module is a fourth resistor group and a third resistor group.

[0019] In one specific implementation, the first resistor within the first voltage divider module satisfies the inequality:

[0020]

[0021] Where j is the number of the first resistors;

[0022] n represents the number of pull-up resistors to be tested;

[0023] R aj_1 Let be the resistance value of the j-th first resistor;

[0024] V DD This refers to the power supply voltage.

[0025] R cn Let n be the resistance value of the nth pull-up resistor to be tested;

[0026] V OL1 The maximum threshold for the low level of the pull-up resistor.

[0027] In one specific implementation, the second resistor within the first voltage divider module satisfies the inequality:

[0028]

[0029] Where k is the number of the second resistors;

[0030] n represents the number of pull-up resistors to be tested;

[0031] R ak_2 Let be the resistance value of the kth second resistor;

[0032] V DD This refers to the power supply voltage.

[0033] R cn Let n be the resistance value of the nth pull-up resistor to be tested;

[0034] V OH1 The minimum threshold for the high level of the pull-up is .

[0035] In one specific implementation, the third resistor within the second voltage divider module satisfies the inequality:

[0036]

[0037] Where l represents the number of the third resistors;

[0038] m represents the number of pull-down resistors to be tested;

[0039] R bl_1 The resistance value of the l-th third resistor;

[0040] V DD This refers to the power supply voltage.

[0041] R dm Let be the resistance value of the m-th pull-down resistor to be tested;

[0042] V OH2 This is the minimum threshold for the high level of the pull-down signal.

[0043] In one specific implementation, the fourth resistor within the second voltage divider module satisfies the inequality:

[0044]

[0045] Where i is the number of the fourth resistors;

[0046] m represents the number of pull-down resistors to be tested;

[0047] R bi_2 Let be the resistance value of the i-th fourth resistor;

[0048] V DD This refers to the power supply voltage.

[0049] R dm Let be the resistance value of the m-th pull-down resistor to be tested;

[0050] V OL2 This is the maximum threshold for the low-level pull-down.

[0051] The present invention also provides a detection card, which adopts the following technical solution:

[0052] A detection card, comprising the detection circuit described above.

[0053] This invention provides a detection method, which adopts the following technical solution:

[0054] A detection method includes the following steps:

[0055] S100: Obtain the datasheet of the boundary scan chip in the DUMMY card and calculate the upper and lower limits of the chip's I / O level thresholds.

[0056] S200, based on the upper and lower limits of the level threshold and the resistance value of the pull-up resistor at the DUT terminal, calculate the resistance values ​​of the first pull-down resistor and the second pull-down resistor connected to the DUT terminal IO in the DUMMY card.

[0057] Based on the upper and lower limits of the level threshold and the resistance value of the pull-down resistor at the DUT terminal, calculate the resistance values ​​of the first pull-up resistor and the second pull-up resistor connected to the DUT terminal IO in the DUMMY card.

[0058] S300, the first pull-down resistor is connected to the DUT terminal IO, the second pull-down resistor is disconnected from the DUT terminal IO, and the IO terminal of the DUMMY card is used for input level detection.

[0059] If the I / O pin of the DUMMY card detects a low level at the detection point of the pull-up resistor at the DUT pin, it indicates that the pull-up resistor at the DUT pin is open.

[0060] If the IO terminal of the DUMMY card detects that the pull-up resistor at the DUT terminal is at a high level, it indicates that the pull-up resistor at the DUT terminal is not open-circuited.

[0061] The first pull-down resistor is disconnected from the DUT's I / O terminal, and the second pull-down resistor is connected to the DUT's I / O terminal. The I / O terminal of the DUMMY card is used for input level detection.

[0062] If the I / O pin of the DUMMY card detects a high level at the detection point of the pull-up resistor at the DUT pin, it indicates that the pull-up resistor at the DUT pin is short-circuited.

[0063] If the IO terminal of the DUMMY card detects that the pull-up resistor at the DUT terminal is at a low level, it indicates that the pull-up resistor at the DUT terminal is not short-circuited.

[0064] The first pull-up resistor is connected to the DUT terminal I / O, and the second pull-up resistor is disconnected from the DUT terminal I / O. The I / O terminal of the DUMMY card is used for input level detection.

[0065] If the I / O pin of the DUMMY card detects a high level at the detection point of the pull-down resistor at the DUT pin, it indicates that the pull-down resistor at the DUT pin is open.

[0066] If the IO terminal of the DUMMY card detects that the detection point of the pull-down resistor at the DUT terminal is low, it indicates that the pull-down resistor at the DUT terminal is not open.

[0067] The first pull-up resistor is disconnected from the DUT's I / O terminal, and the second pull-up resistor is connected to the DUT's I / O terminal. The I / O terminal of the DUMMY card is used for input level detection.

[0068] If the I / O pin of the DUMMY card detects a low level at the detection point of the pull-down resistor at the DUT pin, it indicates that the pull-down resistor at the DUT pin is short-circuited.

[0069] If the IO terminal of the DUMMY card detects that the detection point of the pull-down resistor at the DUT terminal is high, it indicates that the pull-down resistor at the DUT terminal is not short-circuited.

[0070] S400, both the first pull-up resistor and the second pull-up resistor are disconnected from the DUT terminal IO, and the input detection result of the DUMMY card IO terminal is 1;

[0071] The DUT terminal outputs 0, and the DUMMY card's IO terminal detects that the DUT terminal outputs 0.

[0072] The output of 0 at the IO terminal of the DUMMY card indicates that the IO terminal of the DUT is connected normally to the pull-up resistor of the DUT.

[0073] Both the first pull-down resistor and the second pull-down resistor are disconnected from the DUT terminal IO, and the input detection result of the DUMMY card IO terminal is 0;

[0074] The DUT terminal outputs 1 for I / O, and the DUMMY card's I / O terminal detects that the DUT terminal outputs 1 for I / O.

[0075] The DUMMY card outputs 1 at its IO terminal. The DUT terminal's IO terminal detects that the DUMMY card's IO terminal outputs 1, indicating that the connection between the DUT terminal's IO terminal and the DUT terminal's pull-down resistor is normal.

[0076] S500, complete the test based on the test results.

[0077] In summary, the present invention has at least one of the following beneficial technical effects:

[0078] 1. It can perform more accurate and reliable open and short circuit detection on DUT, improving the accuracy and reliability of the results obtained in boundary scan testing;

[0079] 2. It can detect whether there is a short circuit in the DUT's I / O before the DUT performs transmit and receive tests, reducing the risk of the DUT's internal boundary scan chip being burned out and improving the safety of the test.

[0080] 3. It can comprehensively detect the open and short circuits of the pull-up and pull-down resistors of the DUT, as well as the connection between the IO and the pull-up and pull-down resistors, overcoming the problem of obvious errors in the detection results of existing detection methods.

[0081] 4. The DUMMY card, also known as the test card, can both input and output data and is compatible with different DUTs.

[0082] 5. Pull-up testing is performed using a DUMMY card, overcoming the problem of DUTs being unable to be tested. Attached Figure Description

[0083] Figure 1 This is a schematic diagram of the connection between the DUT and the DUMMY card in the background technology.

[0084] Figure 2 This is a schematic diagram of the connection between the DUT and the detection circuit of the present invention.

[0085] Figure 3 This is the open / short circuit detection and control process of the IO pull-up resistor of the DUT in this invention.

[0086] Figure 4 This is the open / short circuit detection and control process of the IO pull-down resistor of the DUT in this invention.

[0087] Figure 5 This is a schematic diagram illustrating the implementation of the controller IO of the present invention connecting multiple novel DUMMY detection cards. Detailed Implementation

[0088] The following is in conjunction with the appendix Figure 1-5 The present invention will be described in further detail below.

[0089] For ease of understanding, please refer to Figure 1 This is a standard DUMMY test card connected to the DUT. The I / O of the boundary scan chip inside the DUT... c1 IO c2 ……IO cn respectively with the pull-up resistor R to be tested c1 R c2 ...R cn Connected, chip I / O d1 IO d2 ……IO dm respectively with the pull-down resistor R to be tested d1 R d2 ...R dm Connected, with n pull-up and m pull-down numbers respectively, IO c1 IO c2 ……IO cn and IO d1 IO d2 ……IO dmConnect to connector M1 inside the DUT. The pins of M1 are c1, c2...cn and d1, d2...dm. The pins c1, c2...cn and d1, d2...dm of connector M1 are respectively connected to the pins a1, a2...an and b1, b2...bm of connector J1 on the conventional boundary scan DUMMY test card, thus connecting the I / O pins of the boundary scan test board. c1 IO c2 ……IO cn and IO d1 IO d1 ……IO dm I / O of a standard boundary scan DUMMY card a1 IO a2 ……IO an and IO b1 IO b2 ……IO bm Connected.

[0090] One detection method is a transmit / receive test:

[0091] First, when the pull-up pin of the DUT is normal, scan the chip I / O within the DUT's inner boundary. c1 IO c2 ……IO cn Output 1, DUMMY card I / O a1 IO a2 ……IO an The corresponding receiver 1, the boundary scan chip IO inside the DUT. c1 IO c2 ……IO cn Output 0, DUMMY card I / O a1 IO a2 ……IO an The corresponding receive is 0.

[0092] When the pull-up switch under test (DUT) is open, the test results are the same as when the pull-up switch is normal. Therefore, this method of transmitting and receiving cannot test whether the pull-up switch under test is open.

[0093] When the pull-up circuit of the DUT is shorted, the DUT inner boundary scan chip I / O is activated. c1 IO c2 ……IO cn Output 1, DUMMY card I / O d1 IO d2 ……IO dm The corresponding receiver 1, the boundary scan chip IO inside the DUT. c1 IO c2 ……IO cn Output 0, DUMMY card I / O a1 IO a2……IO an The reception is unknown, and in addition, IO c1 IO c2 ……IO cn Outputting 0 is equivalent to a short circuit between the power supply inside the DUT and the ground inside the chip. The power supply of the pull-up resistor inside the DUT is the power supply, and its driving capability is very strong. Therefore, in this case, a large current will flow into the boundary scan chip of the DUT at the moment the test data is updated, which poses a risk of burning out the chip.

[0094] Similarly, if the transmit / receive relationship between the DUT and the DUMMY card is reversed, that is, the boundary scan chip IO outputs 0 in the DUMMY card and the IO of the connected DUT receives it, there is a risk of burning out the boundary scan chip in the DUMMY card when the pull-up is short-circuited.

[0095] Therefore, when it is unknown whether the pull-up pin of the DUT is short-circuited, no input / output level transmission / reception tests are performed. That is, the boundary scan chip IO connected to the pull-up pin of the DUT does not output 0, in order to ensure the safety of the test.

[0096] Secondly, when the pull-down mechanism of the DUT is normal, the boundary scan chip I / O within the DUT... d1 IO d1 ……IO dm Output 0, DUMMY card I / O b1 IO b2 ……IO bm The corresponding receive 0, the boundary scan chip IO in the DUT. d1 IO d2 ……IO dm Output 1, DUMMY card I / O b1 IO b2 ……IO bm The corresponding receiver is 1.

[0097] When the pull-down pin under test (DUT) is open, the test results are the same as when it is normal. Therefore, the transmit and receive methods cannot determine whether the pull-down pin under test is open.

[0098] When the DUT is short-circuited by the pull-down switch, the boundary scan chip I / O is activated. d1 IO d1 ……IO dm Output 0, DUMMY card I / O b1 IO b2 ……IO bm The corresponding receive 0, the boundary scan chip IO in the DUT. d1 IO d1 ……IO dmWhen the output is 1, under normal circumstances, the chip's internal source drive capability is weak, and the output of the chip's internal source is pulled low, affecting the DUMMY card's I / O. b1 IO b2 ……IO bm Receiving 0 allows for the detection of a short circuit in the pull-down circuit under test, which is less risky than a short circuit in the pull-up circuit under test. Nevertheless, this situation is equivalent to a short circuit between the power supply inside the boundary scan chip of the DUT and the ground inside the DUT, and the boundary scan chip of the DUT still has a certain risk.

[0099] Similarly, if the transmit / receive relationship between the DUT and the DUMMY card is reversed, that is, the boundary scan chip IO in the DUMMY card outputs 1 and the IO of the connected DUT receives it, the boundary scan chip of the DUMMY card is at risk when the DUT is pulled down and short-circuited.

[0100] Another testing method is input detection:

[0101] First, when the pull-up resistor under test is normal, scan the chip I / O within the inner boundary of the DUT. c1 IO c2 ……IO cn Output 1, DUMMY card I / O a1 IO a2 ……IO an The corresponding receiver 1, the boundary scan chip IO inside the DUT. c1 IO c2 ……IO cn Output 0, DUMMY card I / O a1 IO a2 ……IO an The corresponding receive value will be 0; during the pull-up test, the DUT inner boundary scan chip IO will be used. c1 IO c2 ……IO cn and DUMMY card internal boundary scan chip IO a1 IO a2 ……IO an Input detection can be performed on any input I / O. When the pull-up pin under test (DUT) is normal, the detected level will be 1. When the pull-up pin under test is open, due to the floating I / O, the detected level at both ends of the I / O may be stable at 1, stable at 0, or fluctuate between 0 and 1. Therefore, the probability of false positives in testing is high when the pull-up pin under test is open. When the pull-up pin under test is short-circuited, the input detection level is 1, consistent with the normal test result. Input detection methods cannot detect whether the pull-up pin under test is short-circuited.

[0102] Then, when the pull-down test is normal, the DUT inner boundary scan chip I / O is performed. d1 IO d1……IO dm Output 1, DUMMY card I / O b1 IO b2 ……IO bm The corresponding receiver 1, the boundary scan chip IO inside the DUT. d1 IO d1 ……IO dm Output 0, DUMMY card I / O b1 IO b2 ……IO bm The corresponding receive value will be 0; during the pull-down test of the DUT, the I / O of the chip within the DUT's inner boundary scan will be used. d1 IO d1 ……IO dm and DUMMY card internal boundary scan chip IO b1 IO b2 ……IO bm Input detection can be performed on any input I / O pin. When the pull-down resistor under test (DUT) is normal, the detected level will be 0. When the pull-down resistor under test (DUT) is open, due to the floating pin, the detected level may be stable at 1, stable at 0, or fluctuate between 0 and 1. Therefore, the probability of false positives in open-circuit tests is high. When the pull-down is short-circuited, the input detection level will be 0, consistent with the normal test result. Therefore, the input detection method cannot determine whether the pull-down resistor under test is short-circuited.

[0103] Reference Figure 2 The test card of this application includes a connection module, namely connector J1;

[0104] Pull-up module, i.e., the boundary scan chip I / O of the DUMMY card. a1 IO a2 ……IO ah h is the number of pull-up I / Os of the boundary scan chip inside the DUMMY card, and it is equal to the number of pull-up resistors inside the DUT, i.e., h = n;

[0105] The pull-down module, i.e., the boundary scan chip I / O of the DUMMY card. b1 IO b2 ……IO bg g is the number of pull-down I / Os of the boundary scan chip inside the DUMMY card, and it is equal to the number of pull-down resistors inside the DUT, i.e., g = m.

[0106] Connector J1 is connected to both the upper-level module and the lower-level module; that is, pins a1, a2...ah of the connector are connected to the boundary scan chip I / O within the DUMMY card. a1 IO a2 ……IO ahOne-to-one connection, the connector pins b1, b2...bg are connected to the boundary scan chip I / O within the DUMMY card. b1 IO b2 ……IO bg One-to-one correspondence and connection.

[0107] The measurement circuit also includes a first voltage divider module, including a first resistor group R a1_1 R a2_1 ...R aj_1 j represents the number of first resistors, j = n, meaning the number of first resistors is equal to the number of pull-up resistors in the DUT, and each first resistor corresponds to one pull-up resistor in the DUT; and the second resistor group R a1_2 R a2_2 ...R ak_2 k is the number of second resistors, k = n = j, that is, the number of second resistors is equal to the number of pull-up resistors in the DUT, and each second resistor corresponds to a pull-up resistor in the DUT.

[0108] The second voltage divider module includes the third resistor group R. b1_1 R b2_1 ...R bl_1 l represents the number of the third resistors, and R represents the number of the fourth resistor group. b1_2 R b2_2 ...R bi_2 i represents the number of fourth resistors. The number of third resistors is equal to the number of pull-down resistors in the DUT, i.e., l = m. The number of fourth resistors is equal to the number of pull-down resistors in the DUT, i.e., i = m = l.

[0109] The first control module specifically comprises switch group K1, which controls the connection and disconnection of the first resistor group and connector J1, with each switch corresponding to control one first resistor; and switch group K2, which controls the connection and disconnection of the second resistor group and connector J1, with each switch corresponding to control one second resistor.

[0110] The second control module specifically comprises switch group K3, which controls the connection and disconnection of the fourth resistor group with connector J1, and each switch controls a fourth resistor; and switch group K4, which controls the connection and disconnection of the third resistor group with connector J1, and each switch controls a third resistor.

[0111] The resistance value of the first resistor satisfies the inequality:

[0112]

[0113] Where j is the number of the first resistors;

[0114] n represents the number of pull-up resistors inside the DUT;

[0115] R aj_1Let be the resistance value of the j-th first resistor;

[0116] V DD This refers to the power supply voltage.

[0117] R cn Let be the resistance value of the pull-up resistor inside the nth DUT;

[0118] V OL1 The maximum threshold for the low level of the pull-up resistor.

[0119] The second resistor satisfies the inequality:

[0120]

[0121] Where k is the number of second resistors;

[0122] R ak_2 Let be the resistance value of the k-th second resistor;

[0123] V OH1 The minimum threshold for the high level of the pull-up is .

[0124] The third resistor satisfies the inequality:

[0125]

[0126] Where l represents the number of third resistors;

[0127] m represents the number of pull-down resistors to be tested;

[0128] R dm Let be the resistance value of the pull-down resistor inside the m-th DUT;

[0129] R bl_2 Let be the resistance value of the l-th third resistor;

[0130] V OH2 This is the minimum threshold for the high level of the pull-down signal.

[0131] The fourth resistor satisfies the inequality:

[0132]

[0133] Where i represents the number of fourth resistors;

[0134] R bi_1 Let be the resistance value of the i-th fourth resistor;

[0135] V OL2 This is the maximum threshold for the low-level pull-down.

[0136] When performing pull-up tests on the DUT, first turn on switch group K1 and turn off switch group K2, so that the DUT's I / O... c1 IOc2 ……IO cn Output 1, DUMMY card I / O a1 IO a2 ……IO ah Acquire the signal output by the DUT and detect the acquired signal. If 0 is detected, it indicates that the pull-up of the DUT is open. If 1 is detected, it indicates that the pull-up of the DUT is not open.

[0137] By connecting a larger second resistor R to the DUMMY card terminal a1_2 R a2_2 ...R ak_2 The DUMMY card I / O is divided according to a threshold. When the pull-up resistor inside the DUT is normal, the second resistor R... a1_2 R a2_2 ...R ak_2 It has undertaken no less than V OH1 The voltage is high, and the DUMMY card's IO detects a high level; when the pull-up resistor inside the DUT is open, due to the second resistor R... a1_2 R a2_2 ...R ak_2 When grounded, the DUMMY card's IO detects a low level, while the pull-up resistor inside the DUT will normally be detected as a high level. Therefore, it can effectively detect whether the pull-up resistor is open and has extremely high reliability.

[0138] Then disconnect switch group K1 and turn on switch group K2, which still enables the DUT's I / O. c1 IO c2 ……IO cn Output 1, DUMMY card I / O a1 IO a2 ……IO ah Acquire the signal output by the DUT and detect the acquired signal. If 0 is detected, it indicates that there is no short circuit in the pull-up of the DUT. If 1 is detected, it indicates that there is a short circuit in the pull-up of the DUT.

[0139] By connecting a smaller first resistor R to the DUMMY card terminal a1_1 R a2_1 ...R ak_1 By dividing the voltage of the DUMMY card I / O according to a threshold, the power of the pull-up power supply inside the DUT is cleverly transferred to the first resistor R of the DUMMY card when the pull-up inside the DUT is short-circuited. a1_1 R a2_1 ...R ak_1 Up; when the pull-up resistor inside the DUT is normal, the first resistor R a1_1 R a2_1 ...R ak_1 It bears a responsibility no greater than V OL1The voltage is low, and the DUMMY card's IO detects a low level; when the pull-up resistor inside the DUT is short-circuited, the first resistor R... a1_1 R a2_1 ...R ak_1 It bears the entire VDD voltage, and the DUMMY card's IO detects a low level, thus effectively detecting pull-up short circuits with extremely high reliability, while reducing the risk of boundary scan chip burnout.

[0140] When performing pull-down testing on the DUT, first turn on switch group K3 and turn off switch group K4 to enable the DUT's I / O. d1 IO d2 ……IO dm Output 1, DUMMY card I / O b1 IO b2 ……IO bg Acquire the signal output by the DUT and detect the acquired signal. If a 1 is detected, it indicates that there is an open circuit in the pull-down of the DUT. If a 0 is detected, it indicates that there is no open circuit in the pull-down of the DUT.

[0141] By connecting a larger third resistor R to the DUMMY card terminal b1_1 R b2_1 ...R bl_1 The DUMMY card I / O is divided according to a threshold. When the pull-down resistor of the DUT is normal, the DUT resistor R d1 R d2 ...R dm The voltage between them is not greater than OLV, and the DUMMY card's IO detects a low level; when the DUT pull-down resistor is open, the third resistor R b1_1 R b2_1 ...R bl_1 Because the pull-up is connected to the power supply, the DUMMY card's IO detects a high level, and the pull-down of the DUT under test will definitely detect a low level under normal conditions. Therefore, it can effectively detect whether the internal pull-up of the DUT is open and has extremely high reliability.

[0142] Then disconnect switch group K3 and turn on switch group K4, still enabling the DUT's I / O. d1 IO d2 ……IO dm Output 1, DUMMY card I / O b1 IO b2 ……IO bg Acquire the signal output by the DUT and detect the acquired signal. If 0 is detected, it indicates that there is a short circuit in the pull-down of the DUT. If 1 is detected, it indicates that there is no short circuit in the pull-down of the DUT.

[0143] By connecting a smaller fourth resistor R to the DUMMY card IO terminal b1_2 R b2_2...R bi_2 By dividing the voltage of the DUMMY card I / O according to a threshold, the power of the power supply when the DUT is pulled down and short-circuited is cleverly transferred to the fourth resistor R of the DUMMY card. b1_2 R b2_2 ...R bi_2 Above; when the internal pull-down resistor of the DUT is normal, the internal pull-down resistor R of the DUT d1 R d2 ...R dm The voltage between them is not less than V OH2 The DUMMY card's I / O detects a high level; when the DUT pull-down resistor is short-circuited, the fourth resistor R inside the DUMMY card... b1_2 R b2_2 ...R bi_2 He bore the entire burden of V DD The voltage is low, and the DUMMY card's IO detects a low level, thus effectively detecting pull-down short circuits with extremely high reliability, while reducing the risk of boundary scan chip burnout.

[0144] Example:

[0145] V DD It is 3.3V, V OH1 It is 2.5V, V OL1 The voltage is 0.8V. Two pull-up resistors are used for the DUT, R. c1 and R c2 330Ω and 2000Ω respectively, V OH2 It is 2.5V, V OL2 The voltage is 0.8V. Two pull-down resistors are used for the DUT, R. d1 and R d2 They are 330Ω and 2000Ω respectively.

[0146] When inequalities When it was established, R a1_1 ≤105.6, R a2_ ≤640, take R a1_1 =100Ω, R a2_1 =600Ω. When the DUT is pulled short-circuited, this resistor consumes a significant amount of power. Therefore, it should be chosen as large as possible while meeting the requirements to reduce the power consumption of the DUT's power supply. This cleverly avoids the large current input to the boundary scan chip, thus reducing the testing risk of the boundary scan chip.

[0147] When inequalities When it was established, R a1_2 ≥1031.25, R a2_ ≥6250, take R a1_2 =1100Ω, Ra2_2 =6500Ω. The test results can accurately detect whether the DUT has an open circuit.

[0148] When inequalities When it was established, R b1_ ≥1031.25, R b2_ ≥6250. Take R. a1_1 =100Ω, R a2_1 =600Ω. The test results can accurately detect whether the DUT has an open circuit.

[0149] When inequalities When it was established, R b1_ ≤105.6, R b2_ ≤640. Take R. b1_1 =100Ω, R b2_1 =600Ω. When the DUT is pulled down and short-circuited, the third resistor consumes a significant amount of power. Therefore, this resistor should be chosen as large as possible while meeting the requirements to reduce the power consumption of the DUMMY board. This cleverly avoids the large current output of the boundary scan chip, thus reducing the testing risk of the boundary scan chip.

[0150] In this invention, for ease of control, switch groups K1 and K3 are connected together, and switch groups K2 and K4 are connected together. That is, switch groups K1 and K3 switch synchronously, and switch groups K2 and K4 switch synchronously. This facilitates simultaneous detection of the pull-up and pull-down of the DUT, improving detection efficiency.

[0151] Reference Figure 3 and Figure 4 The present invention also discloses a detection method using the above-mentioned detection card, comprising the following steps:

[0152] S100, obtain the datasheet of the boundary scan chip in the DUMMY card, calculate the upper and lower limits of the chip's I / O level thresholds, that is, calculate V. OH1 V OL、 V OH2 and V OL2 .

[0153] S200, based on V OH1 V OL、 V OH2 and V OL2 And the resistance value R of the pull-up resistor at the DUT terminal. c1 R c2 ...R cn Calculate the resistance values ​​of the first and second resistors connected to the DUT terminal IO within the DUMMY card, i.e., R.a1_1 R a2_1 ...R ak_1 and R a1_2 R a2_2 ...R ak_2 .

[0154] Based on V OH1 V OL、 V OH2 and V OL2 and the resistance value R of the pull-down resistor at the DUT terminal. d1 R d2 ...R dm Calculate the resistance values ​​of the third and fourth resistors connected to the DUT terminal IO inside the DUMMY card, i.e., R. b1_1 R b2_1 ...R bl_1 and R b1_2 R b2_2 ...R bi_2 .

[0155] S300 turns on switch groups K1 and K3, and turns off switch groups K2 and K4. The DUMMY card's I / O pins are used for input level detection.

[0156] If the DUMMY card's IO a1 IO a2 ……IO ah The pull-up resistor R at the DUT terminal was detected. c1 R c2 ...R cn A low level at the detection point indicates that the pull-up pin of the DUT I / O is open.

[0157] If the DUMMY card's IO a1 IO a2 ……IO ah The pull-up resistor R at the DUT terminal was detected. c1 R c2 ...R cn The detection point is high, indicating that the pull-up of the DUT terminal IO is not open.

[0158] If the DUMMY card's IO b1 IO b2 ……IO bg The pull-down resistor R at the DUT terminal was detected. d1 R d2 ...R dm The detection point is low, indicating that the pull-down of the DUT terminal IO is not open.

[0159] If the DUMMY card's IO b1 IO b2……IO bg The pull-down resistor R at the DUT terminal was detected. d1 R d2 ...R dm The detection point is high, indicating that the pull-down of the DUT terminal IO is open.

[0160] Disconnect switch groups K1 and K3, and connect switch groups K2 and K4. The DUMMY card's I / O pins will then perform input level detection.

[0161] If the DUMMY card's IO a1 IO a2 ……IO ah The pull-up resistor R at the DUT terminal was detected. c1 R c2 ...R cn The detection point is low, indicating that the pull-up pin of the DUT I / O is not short-circuited.

[0162] If the DUMMY card's IO a1 IO a2 ……IO ah The pull-up resistor R at the DUT terminal was detected. c1 R c2 ...R cn The detection point is high, indicating that the pull-up of the DUT terminal IO is not short-circuited.

[0163] If the DUMMY card's IO b1 IO b2 ……IO bg The pull-down resistor R at the DUT terminal was detected. d1 R d2 ...R dm The detection point is low, indicating that the pull-down short circuit of the DUT terminal IO.

[0164] If the DUMMY card's IO b1 IO b2 ……IO bg The pull-down resistor R at the DUT terminal was detected. d1 R d2 ...R dm The detection point is high, indicating that the pull-down short circuit of the DUT terminal IO.

[0165] S400, based on the above test results, if the pull-up and pull-down resistors at the DUT end are short-circuited or open-circuited, it indicates a high risk of chip burnout during the transmit / receive test, and the transmit / receive test cannot be performed. If neither the pull-up nor pull-down resistors at the DUT end are short-circuited or open-circuited, it indicates that the transmit / receive test is safe and can be performed.

[0166] First resistor Ra1_1 R a2_1 ...R ak_1 Second resistor R a1_2 R a2_2 ...R ak_2 All connections to the DUT's I / O pins are disconnected. The DUT's I / O pins output 0. The DUMMY card's I / O pins detect that the DUT's I / O pins output 0, indicating that the DUT's I / O pins are disconnected from the DUT's pull-up resistor R. c1 R c2 ...R cn The connection is normal. When the DUT segment's I / O has no output condition, only an input condition, the DUMMY card's I / O output is 0. The DUT's I / O detects the DUMMY card's I / O output being 0, indicating that the DUT's I / O is not connected to the DUT's pull-up resistor R. c1 R c2 ...R cn Connection is normal.

[0167] Third resistor R b1_1 R b2_1 ...R bl_1 and the fourth resistor R b1_2 R b2_2 ...R bi_2 When all connections to the DUT's I / O are disconnected, the DUT's I / O outputs 1, and the DUMMY card's I / O detects this output, indicating that the connection between the DUT's I / O and the DUT's pull-down resistor is normal. When the DUT's I / O has no output condition but only an input condition, the DUMMY card's I / O outputs 1, and the DUT's I / O detects this output, also indicating that the connection between the DUT's I / O and the DUT's pull-down resistor is normal.

[0168] S500, complete the test based on the test results.

[0169] It should be noted that, for ease of understanding, the pull-up and pull-down tests are shown separately in the accompanying drawings. The above test methods need to be performed before the transmit and receive tests. Furthermore, the open and short circuit tests for pull-up and pull-down can be performed separately. In this invention, for ease of testing, switch groups K1 and K3, and switch groups K2 and K4 are connected in series to form CTR_IO1 and CTR_IO2, enabling switch groups K1 and K3 to switch synchronously, and switch groups K2 and K4 to switch synchronously.

[0170] Furthermore, in actual testing, the DUT has many interfaces similar to M1, most of which are commonly used standard connector interfaces, such as MCIO, SLIM, DDR, SATA, PCIE, OCP, etc. Each standard connector is equipped with a standard DUMMY card for mating test with the DUT connector. These interfaces have pins that are the same as or similar to those in this invention and need to be tested. Moreover, the fixed positions of these pins are defined in a fixed way. For this type of pin, a new standardized DUMMY test card needs to be redesigned. That is, two sets of controllable pull-up or pull-down pins are connected to the corresponding DUMMY card IO position according to the above method, and the test is controlled separately.

[0171] Combination Figure 5 As shown, there are many connectors similar to M1 inside the DUT, and these connectors all need to be tested using a DUMMY card. Figure 5 The cascading relationship of the new DUMMY cards 1 to p is demonstrated. The connector within each new DUMMY card mates with the connector on the DUT. Following the M1 connector classification method, the short-circuit and open-circuit tests for pull-up and pull-down switches are independently controlled by the CTR_IO1 and CTR_IO2 signals, respectively. First, the switch group controlled by CTR_IO1 is turned on, and the switch group controlled by CTR_IO2 is turned off to perform the first test. Then, the switch group controlled by CTR_IO1 is turned off, and the switch group controlled by CTR_IO2 is turned on to perform the second test. This is a two-step variable test. Figure 5 As can be seen, the CTR_IO1 and CTR_IO2 signal lines have the same routing as the TCK and TMS lines. Therefore, they can be cascaded to the controller in the same way as the TCK and TMS signals of JTAG, which is very convenient to implement.

[0172] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A detection circuit, comprising a board under test (BUT), a detection card for detecting the BUT, a connection module, a pull-up module, and a pull-down module, wherein the pull-up module and the pull-down module are both connected to the detection card, and the detection card is connected to the BUT via the connection module, characterized in that: It also includes a first voltage divider module, which is connected to the connection module and the pull-up module, to distribute the voltage in the circuit when the circuit is short-circuited or open-circuited; A first control module is connected to the first voltage divider module and controls the conduction between the first voltage divider module and the connection module and the pull-up module. The second voltage divider module is connected to the connection module and the pull-down module, and distributes the voltage in the circuit when the circuit is short-circuited or open-circuited. The second control module is connected to the second voltage divider module and controls the connection between the second voltage divider module and the connection module and the pull-down module. The first voltage divider module includes a first resistor group and a second resistor group, and the second voltage divider module consists of a fourth resistor group and a third resistor group; The first resistor in the first voltage divider module satisfies the inequality: Where j is the number of the first resistors; n represents the number of pull-up resistors to be tested; R aj_1 Let be the resistance value of the j-th first resistor; V DD The power supply voltage for the detection card; R cn Let n be the resistance value of the nth pull-up resistor to be tested; V OL1 The maximum threshold for the low level of the pull-up resistor.

2. The detection circuit according to claim 1, characterized in that: Both the first control module and the second control module are switch groups.

3. The detection circuit according to claim 1, characterized in that: The second resistor in the first voltage divider module satisfies the inequality: Where k is the number of the second resistors; n represents the number of pull-up resistors to be tested; R ak_2 Let be the resistance value of the kth second resistor; V DD The power supply voltage for the detection card; R cn Let n be the resistance value of the nth pull-up resistor to be tested; V OH1 The minimum threshold for the high level of the pull-up is .

4. The detection circuit according to claim 1, characterized in that: The third resistor within the second voltage divider module satisfies the inequality: Where l represents the number of the third resistors; m represents the number of pull-down resistors to be tested; R bl_1 The resistance value of the l-th third resistor; V DD The power supply voltage for the detection card; R dm Let m be the resistance value of the m-th pull-down resistor to be tested; V OH2 This is the minimum threshold for the high level of the pull-down signal.

5. The detection circuit according to claim 1, characterized in that: The fourth resistor in the second voltage divider module satisfies the inequality: Where i is the number of the fourth resistors; m represents the number of pull-down resistors to be tested; R bi_2 Let be the resistance value of the i-th fourth resistor; V DD The power supply voltage for the detection card; R dm Let be the resistance value of the m-th pull-down resistor to be tested; V OL2 This is the maximum threshold for the low-level pull-down.

6. A detection card, characterized in that: Includes the detection circuit described in any one of claims 1 to 5.

7. A detection method, characterized in that: The detection circuit is executed by a detection circuit, which includes a board under test, a detection card for detecting the board under test, a connection module, a pull-up module, and a pull-down module. The pull-up module and the pull-down module are both connected to the detection card. The detection card is connected to the board under test through the connection module. The circuit also includes a first voltage divider module, which is connected to the connection module and the pull-up module to distribute the voltage in the circuit when the circuit is short-circuited or open-circuited. The detection card is a DUMMY card; A first control module is connected to the first voltage divider module and controls the conduction between the first voltage divider module and the connection module and the pull-up module. The second voltage divider module is connected to the connection module and the pull-down module, and distributes the voltage in the circuit when the circuit is short-circuited or open-circuited. The second control module is connected to the second voltage divider module and controls the connection between the second voltage divider module and the connection module and the pull-down module. The first voltage divider module includes a first resistor group and a second resistor group, and the second voltage divider module consists of a fourth resistor group and a third resistor group; The method includes the following steps: S100: Obtain the datasheet of the boundary scan chip in the DUMMY card and calculate the upper and lower limits of the chip's I / O level thresholds. S200, based on the upper and lower limits of the level threshold and the resistance value of the pull-up resistor at the DUT terminal, calculate the resistance values ​​of the first pull-down resistor and the second pull-down resistor connected to the DUT terminal IO in the DUMMY card. Based on the upper and lower limits of the level threshold and the resistance value of the pull-down resistor at the DUT terminal, calculate the resistance values ​​of the first pull-up resistor and the second pull-up resistor connected to the DUT terminal IO in the DUMMY card. S300, the first pull-down resistor is connected to the DUT terminal IO, the second pull-down resistor is disconnected from the DUT terminal IO, and the IO terminal of the DUMMY card is used for input level detection. If the I / O pin of the DUMMY card detects a low level at the detection point of the pull-up resistor at the DUT pin, it indicates that the pull-up resistor at the DUT pin is open. If the IO terminal of the DUMMY card detects that the pull-up resistor at the DUT terminal is at a high level, it indicates that the pull-up resistor at the DUT terminal is not open-circuited. The first pull-down resistor is disconnected from the DUT's I / O terminal, and the second pull-down resistor is connected to the DUT's I / O terminal. The I / O terminal of the DUMMY card is used for input level detection. If the I / O pin of the DUMMY card detects a high level at the detection point of the pull-up resistor at the DUT pin, it indicates that the pull-up resistor at the DUT pin is short-circuited. If the IO terminal of the DUMMY card detects that the pull-up resistor at the DUT terminal is at a low level, it indicates that the pull-up resistor at the DUT terminal is not short-circuited. The first pull-up resistor is connected to the DUT terminal I / O, and the second pull-up resistor is disconnected from the DUT terminal I / O. The I / O terminal of the DUMMY card is used for input level detection. If the I / O pin of the DUMMY card detects a high level at the detection point of the pull-down resistor at the DUT pin, it indicates that the pull-down resistor at the DUT pin is open. If the IO terminal of the DUMMY card detects that the detection point of the pull-down resistor at the DUT terminal is low, it indicates that the pull-down resistor at the DUT terminal is not open. The first pull-up resistor is disconnected from the DUT's I / O terminal, and the second pull-up resistor is connected to the DUT's I / O terminal. The I / O terminal of the DUMMY card is used for input level detection. If the I / O pin of the DUMMY card detects a low level at the detection point of the pull-down resistor at the DUT pin, it indicates that the pull-down resistor at the DUT pin is short-circuited. If the IO terminal of the DUMMY card detects that the detection point of the pull-down resistor at the DUT terminal is high, it indicates that the pull-down resistor at the DUT terminal is not short-circuited. S400, both the first pull-up resistor and the second pull-up resistor are disconnected from the DUT terminal IO, and the input detection result of the DUMMY card IO terminal is 1; The DUT terminal outputs 0, and the DUMMY card's IO terminal detects that the DUT terminal outputs 0. The output of 0 at the IO terminal of the DUMMY card indicates that the IO terminal of the DUT is connected normally to the pull-up resistor of the DUT. Both the first pull-down resistor and the second pull-down resistor are disconnected from the DUT terminal IO, and the input detection result of the DUMMY card IO terminal is 0; The DUT terminal outputs 1 for I / O, and the DUMMY card's I / O terminal detects that the DUT terminal outputs 1 for I / O. The DUMMY card outputs 1 at its IO terminal. The DUT terminal's IO terminal detects that the DUMMY card's IO terminal outputs 1, indicating that the connection between the DUT terminal's IO terminal and the DUT terminal's pull-down resistor is normal. S500, complete the test based on the test results.

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