Memory incorporating logic LSI and method for testing the same LSI

Abstract: This invention relates to a memory incorporating logic LSI and a method for testing the same LSI. Signal path switching circuit portions (50, 51) are disposed in the course of a memory portion (30) and a logic circuit portion (20) so that a test signal input and an output signal can be observed at the input and output terminal portion (40) so as to be able to effect a dynamic function test of the memory portion (30). Further there is disposed a logic circuit testing signal memory circuit portion (80), which switches over the signal path switch­ ing circuit portions (50, 51) to the logic circuit portion (20) so as to be able to effect a test of the logic circuit portion (20), independently of the state of the memory portion (30)

Description: BACKGROUND OF THE INVENTION This invention relates to a memory incorporating logic LSI, in particular to a memory incorporating logic LSI provided with a circuit for testing it and a method for testing the same LSI. Advanced testing techniques for structured ASIC products have been published previously. In the "Proceedings of the IEEE 1986, Custom Integrated Circuits Conference", pages 412-415 a set of scanning schemes is discussed, which allows megacell and memory structures of an ASIC to be tested by utilizing a plurality of latches. Another way of testing the memory portion in a memory incorporating logic LSI was disclosed in JP-B-57-3107. A scan-in to a flipflop is utilized by applying a part of input pattern to a flip-flop provided with scanning function and the rest to an input terminal. In JP-A-61-204744 (corresponding US-A-4,710,930) by the same inventors, a method, by which the memory portion is provided with scanning function and scan-in and scan-out to and from the memory portion are utilized, has been discussed. According to all the prior art techniques described above, since the test has been effected by utilizing scanning function, there has been a problem that dynamic function test cannot be effected, by which the test is effected with a speed similar to that at the real operation time. As a method to solve this problem, a method is conceivable, by which all the input and output signal lines of the memory are connected with external terminals (input and output terminal portion). However, by this method another problem is produced that many external terminals are necessary for the LSI. In JP-A-60-171735 therefor a change-over gate circuit was suggested for transmitting a memory access signal from an input Di of the integrated circuit to the memory, by which the logic circuitry can be switched off and can be by-passed. Accordingly a memory test is rendered feasible without additional external terminals. However, in JP-A-60-171735 it is not revealed how the testing of the LSI can best be performed by a predetermined test pattern that is entered through a terminal and that is processed by the logic circuitry. The object of this invention is to provide a memory incorporating logic LSI and a method for testing the same LSI, with which it is possible to effect a dynamic function test of the memory portion without increasing the number of external terminals of the LSI and further to effect easily the test of the logic circuit portion. This object is achieved as indicated in claims 1 and 6. SUMMARY OF THE INVENTION Firstly a memory incorporating logic LSI provided with an input and output terminal portion, a memory portion, a logic circuit portion, a first signal path, through which a signal is transmitted from the logic circuit portion to the memory portion, and a second signal path, through which the signal is transmitted from the memory portion to the logic circuit portion, comprises an operation mode input circuit portion, which inputs an operation mode signal determining the operational state of the memory incorporating logic LSI through the input and output terminal portion; a memory test input signal path, with which the input and output terminal portion is connected and through which a signal for memory test is inputted and transmitted, a memory test output signal path, which outputs the output signal from the memory portion to the input and output terminal portion; and a signal path switching circuit portion disposed in the course of the first signal path, which transmits the signal from the memory test input signal path by switching off the first signal path from the logic circuit portion on the basis of the operation mode signal. Secondly a memory incorporating logic LSI according to this invention comprises an operation mode input circuit portion, which inputs an operation mode signal determining the operational state of the memory incorporating logic LSI through the input and output terminal portion, a logic circuit testing signal memory circuit portion having an output portion outputting a predetermined logic circuit test pattern inputted from the input and output terminal portion, which inputs a signal outputted from the logic circuit portion to the first signal path and outputs it to the input and output terminal portion, and a signal path switching circuit portion disposed in the course of the second signal path, which transmits the signal from the output portion of the logic circuit testing signal memory circuit portion by switching off the second signal path from the memory portion on the basis of the operation mode signal. Thirdly a memory incorporating logic LSI according to this invention comprises a memory test input signal path, with which the input and output terminal portion is connected and through which a signal for memory test is inputted and transmitted, a memory test output signal path, which outputs the output signal from the memory portion to the input and output terminal portion, a logic circuit testing signal memory circuit portion having an output portion outputting a predetermined logic circuit test pattern inputted from the input and output terminal portion, which inputs a signal outputted from the logic circuit portion to the first signal path and outputs it to the input and output terminal portion, and signal path switching circuit portions disposed in the course of the first and the second signal paths, which transmits the signal from the memory test input signal path by switching off the first signal path from the logic circuit portion, when the operation mode signal is at the memory test mode, and the signal from the output portion of the logic circuit testing signal memory circuit portion by switching off the second signal path from the memory portion, when the operation mode signal is at the logic circuit test mode. Fourthly a method for testing a memory incorporating logic LSI according to this invention is characterized in that the operation mode signal determining the operation mode is inputted to select either one of the memory test and the logic circuit test; the signal path is switched over in the signal path switching circuit portions; a predetermined test signal is inputted from the input and output terminal portion; the result of the test effected by inputting the test signal is observed in the input and output terminal portion; and information obtained by observing the result is compared with predetermined expected information in order to test the memory portion and the logic circuit portion. Now the operation of the construction described above will be explained. The signal path switching circuit portion switches the signal path between the first and the second signal paths on the basis of the operation mode signal inputted from the operation mode input circuit portion. When the operation mode signal indicate a memory test, the first signal path is switched from the logic circuit portion to the memory test input signal path connected with the input and output terminal portion. The memory test input signal path inputs a memory test signal from the exterior to the memory portion and transmits the result of the test of the memory portion to the input and output terminal portion through the memory test output signal path. When the operation mode signal indicates a logic circuit test, the second signal path is switched from the memory portion to the output portion of the logic signal test signal memory circuit portion. The logic circuit test signal memory circuit portion receives a signal outputted from the logic circuit portion stated above to the first signal path and outputs it to the input and output terminal portion. It outputs also a predetermined logic circuit test pattern, inputted from the input and output terminal portion, from the output portion to the logic circuit portion stated above through the second signal path. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit diagram showing the circuit construction of a memory incorporating logic LSI, which is an embodiment of this invention; Figs. 2a and 2b show two different circuit constructions of a signal path switching circuit portion; Fig. 3 shows a circuit construction of a switch control signal generating circuit; Figs. 4a to 4d show four different circuit constructions of the signal path switching circuit portion, which is used in common as an external terminal. Fig. 5 is a timing chart of signals at the test of the memory portion; and Fig. 6 is a timing chart of signals at the test of the logic circuit portion. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinbelow an embodiment of this invention will be explained, referring to Figs. 1 to 6. Fig. 1 is a block diagram illustrating the circuit construction of a memory incorporating logic LSI 10 according to this invention. The memory incorporating LSI 10 includes a logic circuit portion 20 consisting of combined logic elements determining an output signal according to predetermined logics, responding to an input signal, and memory logic elements determining the output signals, based on the input signals and the internal state, and an input and output terminal portion 40, which transmits and receives input and output signals from and to the exterior. There are disposed switching circuit portions (signal path switching circuit portions) 50 and 51 for switching over groups of signal lines in a group of signal lines (first signal path) 108, 109 transmitting the signal from the logic circuit portion 20 to the memory portion 30 and a group of signal lines (second signal path) 106, 107 transmitting the signal from the memory portion 30 to the logic circuit portion 20, respectively. Figs. 2a and 2b show two different examples of the circuit construction of the switching circuit within the switching circuit portions 50 and 51. In the switching circuit 50a indicated in Fig. 2a, in the case where the value of a switch control signal line 70 has a logic value '0', since the output of an AND gate 211 has a logic value '0', the value in a signal line 111a within a group of signal line (memory test input signal path) 111 appears at the output of an OR gate 221, which value is supplied to signal lines 109a, 113a within groups of signal lines 109, 113. The operation of the switching circuit 51a indicated in Fig. 2b is identical to that described above. Switch control signal lines 70 and 71 are fed by a switch control signal generating circuit 90. Fig. 3 shows an example of the circuit construction of the switch control signal generating circuit 90. In the switch control signal generating circuit 90 indicated in Fig. 3, when the value in a signal line 101 is '1', both the values in switch control signal lines 70 and 71 are '1', and when the value in the signal line 101 is '0', the values in the switch control signal lines 70 and 71 are '1' and '0', respectively, in the case where the value in a signal line 100 is '0', and '0' and '1', respectively, in the case where the value in the signal line 100 is '1'. The signal lines 100 and 101 are fed with signals by a switch control terminal and a mode control terminal within operation mode input circuit portions 60 and 61. Consequently it is possible to set directly the values in the switch control signal lines 70 and 71 from the exterior through the switch control signal generating circuit 90. In addition, the memory incorporating logic LSI 10 includes a testing flipflop portion (logic circuit test signal memory circuit portion) 80. Now a method for testing the memory incorporating logic LSI 10 according to this invention indicated in Fig. 1 will be explained. At first a method for testing the memory portion 30 and then a method for testing the logic circuit portion 20 will be explained. The test of the memory portion 30 of the memory incorporating logic LSI 10 is effected as follows. At the test of the memory portion 30, '0' is applied to the mode control terminal in the operation mode input circuit portion 61 and '1' is applied to the switch control terminal in the operation mode input circuit portion 6 continuously. In this way, since the values in the switch control signal lines 70 and 71 are '0' and '1', respectively, values in the group of signal lines 111 are supplied to the group of signal lines 109 in the switching circuit portion 50 and values in the group of signal lines 106 are supplied to the group of signal lines 110 in the switching circuit portion 51. Fig. 5 shows a timing chart indicating transmission of the signals at the test of the memory portion 30. That is, at the test of the memory portion 30, the logic value 111a′ in the signal line 111a within the group of signal lines 111 inputted from the input and output terminal portion 40 appears as the logic value 109a′ in the signal line 109a within the group of input signal lines 109 as it is, and the logic value 106a′ in the signal line 106a within the group of output signal lines 106 from the memory portion 30 appears as the logic value 110a′ in the signal line 110a within the group of signal lines 110 outputted to the input and output terminal portion 40 as it is. It is thus indicated that logic values 108a′, 112a′ in the signal lines 108a, 112a within the groups of signal lines 108, 112 has no influences on the others. Consequently the test of the memory portion 30 is effected by applying an input pattern to the input terminal in the input and output terminal portion 40 connected with the groups of signal lines 102, 111 and comparing an output pattern observed at the output terminal in the input and output terminal portion 40 connected with the groups of signal lines 103, 110 with an expected pattern. In this way, according to this embodiment, since at the test of the memory portion 30 all the input and output signals to and from the memory portion 30 can be controlled and observed from the exterior, an effect is obtained that the memory portion 30 can be tested with a working speed identical to that at the real operation. Next the test of the logic circuit portion 20 of the memory incorporating logic LSI 10 is effected as follows. At the test of the logic circuit portion 20 '0' is applied to the mode control terminal in the operation mode input circuit portion 61 and '0' is applied to the switch control terminal in the operation mode input circuit portion 60 continuously. In this way, since the values in the switch control signal lines 70 and 71 are '1' and '0', respectively, values in the group of signal lines 108 are supplied to the group of signal lines 113 in the switching circuit portions 50 and values in the group of signal lines 112 are supplied to the group of signal lines 107 in the switching circuit portion 51. Fig. 6 shows a timing chart indicating transmission of the signals at the test of the logic circuit portion 20. That is, at the test of the logic circuit portion 20, the logic value 112a′ in the signal line 112a within the group of signal lines 112 coming from the testing flipflop portion 80 appears as the logic value 107a′ in the signal line 107a within the group of input signal lines 107 as it is, and the logic value 108a′ in the signal line 108a within the group of output signal lines 108 from the logic circuit portion 20 appears as the logic value 113a′ in the signal line 113a within the group of signal lines 113 to the testing flipflop portion 80 as it is. It is thus indicated that logic values 106a′, 111a′ in the signal lines 106a, 111a within the groups of signal lines 106, 111 has no influences on the others. Consequently the test of the logic circuit portion 20 is effected by applying a pattern of the input pattern to the input terminal in the input and output terminal portion40 connected with the group of signal lines 104, at the same time setting the remaining part of the input pattern to the flipflop having a scanning function within the testing flipflop portion 80 by means of a scan-in 114 and comparing the output pattern observed at the output terminal in the input and output terminal portion 40 connected with the group of signal lines 105 and the pattern scanned-out 115 from the flipflop having a scanning function within the testing flipflop portion 80 with an expected pattern. In this way, according to this embodiment, since at the test of the logic circuit portion 20 it is not necessary at all to take the state of the memory portion 30 into account, an effect is obtained that a test pattern for the logic circuit portion 20 can be easily formed. Figs. 4a to 4d show four examples of the circuit construction, in the case where an external terminal used for the test of the memory portion 30 is used in common as an external terminal used for the usual operation. Fig. 4a shows the circuit construction in the case where the input terminal used for the usual operation is used in common as the input terminal for the test of the memory portion. In this case, at the usual operation and at the test of the logic circuit portion 20 the signal is sent to the signal line 104a supplying the input signal from the external terminal 300 to the logic circuit portion 20 through an input buffer gate 400. On the contrary, at the test of the memory portion 30, the signal is sent to the signal line 11a supplying the memory portion testing input signal through another input buffer gate 401. Fig. 4b shows the circuit construction in the case where the input terminal used for the usual operation is used in common as the output terminal for the test of the memory portion. In this case, at the usual operation and at the test of the logic circuit portion 20 the value in the switch control signal line 71 giving the control signal of the output buffer gate 500 is '0'. Consequently the output of the output buffer gate 500 is in the high impedance state and a signal is sent to the input signal line 104b from the external terminal 301 to the logic circuit portion 20 through an input buffer gate 402. Therefore, at the test of the memory portion 30, since the value in the switch control signal line 71 is turned to '1', a signal is sent from the memory testing output signal line 110b to the external terminal 301 through the output buffer gate 500. Fig. 4c shows the circuit construction in the case where the output terminal used for the usual operation is used in common as the input terminal for the test of the memory portion. In this case, at the usual operation and at the test of the logic circuit portion 20, since the value in the switch control signal line 71 is '0' and therefore the output value of a NOT gate 204 is '1', a signal is sent from the output signal line 105c of the logic circuit portion 20 to the external terminal 302 through a buffer gate 501. On the contrary, at the test of the memory portion 30, since the value in the switch control signal line 71 is '1', the output value of the NOT gate 204 is '0'. Consequently the output of the output buffer gate 501 is in the high impedance state and a signal is sent from the external terminal 302 to the memory portion testing input signal line 111c through an input buffer gate 403. Fig. 4d shows the circuit construction in the case where the output terminal used for the usual operation is used in common as the output terminal for the test of the memory portion. In this case, at the usual operation and at the test of the logic circuit portion 20 the value in the switch control signal line 71 is '0' and it is '1' at the test of the memory portion 30. Consequently, at the usual operation and at the test of the logic circuit portion 20, since the output value of the output buffer gate 503 is in the high impedance state, the signal is sent from the output signal line 105d of the logic circuit portion 20 to the external terminal 303 through the output buffer gate 502. On the contrary, at the test of the memory portion 30, since the output value of the output buffer gate 502 is in the impedance state, the signal is sent from the output line 110d for the test of the memory portion to the external terminal 303 through the output buffer gate 503. According to the embodiments of this invention indicated in Figs. 4a to 4d an effect can be obtained that the increase in the number of external terminals is small, because the external terminals used for the test of the memory portion is used in common as those used for the usual operation. According to this invention, in a memory incorporating logic LSI, by disposing signal path switching circuit portions in the course of signal paths between the memory portion and the logic circuit portion, since at the test of the memory portion it is possible to switch-on the signal paths effecting the test signal input to the memory portion and the observation of the output signal from the memory portion at the input and output terminal portion, the dynamic function test of the memory portion is possible owing to the signal path switching circuit portion. Further, since at the test of the logic circuit portion it is possible to switch over the signal path from the output signal path from the memory portion to the signal path from the logic circuit test signal memory circuit portion so as to input the signal in the logic circuit portion, an excellent effect can be obtained that it is possible to effect the test of the logic circuit portion, independently of the state of the memory portion, and thus formation of the test pattern is made easier.

Claims: A memory incorporating logic LSI comprising: an input and output terminal portion (40), which transmits and receives input and output signals from and to the exterior; a memory portion (30) to and from which memory information is written and read out from and to the exterior through said input and output terminal portion (40); a logic circuit portion (20), which determines one of said output signals according to a predetermined logic, responding to one of said input signals; a first signal path (108, 109), connecting said logic circuit portion (20) to said memory portion (30) and being serially composed of a logic circuit output path (108) and a memory portion input path (109); a second signal path (106, 107) connecting said memory portion (30) to said logic circuit portion (20) and being serially composed of a memory portion output path (106) and a logic circuit input path (107); operating mode input circuit portions (60, 61), which input operation mode signals determining the operational state of said memory incorporating logic LSI (10) through said input and output terminal portion (40); a memory test input signal path (111), connecting said input and output terminal portion (40) with said memory portion input path (109) and through which a signal for memory test is inputted and transmitted; a memory test output signal path (110), connecting said memory portion output path (106) to said input and output terminal portion (40); a logic circuit testing signal memory circuit portion (80), an output portion of which outputs predetermined logic circuit test pattern (112) inputted from a terminal (114) of said input and output terminal portion (40), where said logic circuit testing signal memory circuit portion (80) receives a signal (113) from said logic circuit output path (108) of said logic circuit portion (20) and outputs it to a terminal (115) of said input and output terminal portion (40); a first signal path switching circuit portion (50) disposed between said logic circuit output path (108) and the memory portion input path (109), which transmits the signal from said memory test input signal path (111) to the memory portion (30) by switching off said signal (113) from said logic circuit output path (108) from said logic circuit portion (20), when said operation mode is the memory test mode, and also transmits said signal (113) from said logic circuit output path (108) to said logic circuit testing signal memory circuit portion (80), when said operation mode is the logic circuit test mode; and a second signal path switching circuit portion (51) disposed between the memory portion output path (106) and the logic circuit input path (107), which transmits the signal from the memory portion (30) to said memory test output signal path (110) by switching off said logic circuit input path (107) to said logic circuit portion (20) from said logic circuit test pattern (112), when said operation mode is the memory test mode, and also transmits said logic circuit test pattern (112) from said output portion of said logic circuit testing signal memory circuit portion (80) to the logic circuit portion (20) by switching off said memory portion output path (106) from said memory portion (30), when said operation mode is the logic circuit test mode. A memory incorporating logic LSI according to claim 1, wherein an input terminal, which applies a test signal from the exterior to said memory test input signal path (111), is used in common as an input terminal, through which a signal is inputted from the exterior to said logic circuit portion (20) at the usual operation. A memory incorporating logic LSI according to claim 1, wherein an output terminal, which outputs a signal from said memory test output signal path (110) to the exterior, is used in common as an input terminal, through which a signal is inputted from the exterior to said logic circuit portion (20) at the usual operation. A memory incorporating logic LSI according to claim 1, wherein an input terminal, which applies a test signal from the exterior to said memory test input signal path (111), is used in common as an output terminal, through which a signal is outputted from said logic circuit portion (20) to the exterior at the usual operation. A memory incorporating logic LSI according to claim 1, wherein an output terminal, which outputs a signal from said memory test output signal path (110) to the exterior, is used in common as an output terminal, through which a signal is outputted from said logic circuit portion (20) to the exterior at the usual operation. A method for testing a memory incorporating logic LSI comprising: an input and output terminal portion (40), which transmits and receives input and output signals from and to the exterior; a memory portion (30) to and from which memory information is written and read out from and to the exterior through said input and output terminal portion (40); a logic circuit portion (20), which determines one of said output signals according to a predetermined logic, responding to one of said input signals; a first signal path (108, 109), connecting said logic circuit portion (20) to said memory portion (30) and being serially composed of a logic circuit output path (108) and a memory portion input path (109); a second signal path (106, 107) connecting said memory portion (30) to said logic circuit portion (20) and being serially composed of a memory portion output path (106) and a logic circuit input path (107); operating mode input circuit portions (60, 61), which input operation mode signals determining the operational state of said memory incorporating logic LSI (10) through said input and output terminal portion (40); a memory test input signal path (111), connecting said input and output terminal portion (40) with said memory portion input path (109) and through which a signal for memory test is inputted and transmitted; a memory test output signal path (110), connecting said memory portion output path (106) to said input and output terminal portion (40); a logic circuit testing signal memory circuit portion (80), an output portion of which outputs predetermined logic circuit test pattern (112) inputted from a terminal (114) of said input and output terminal portion (40), where said logic circuit testing signal memory circuit portion (80) receives a signal (113) from said logic circuit output path (108) of said logic circuit portion (20) and outputs it to a terminal (115) of said input and output terminal portion (40); a first signal path switching circuit portion (50) disposed between said logic circuit output path (108) and the memory portion input path (109), which transmits the signal from said memory test input signal path (111) to the memory portion (30) by switching off said signal (113) from said logic circuit output path (108) from said logic circuit portion (20), when said operation mode is the memory test mode, and also transmits said signal (113) from said logic circuit output path (108) to said logic circuit testing signal memory circuit portion (80), when said operation mode is the logic circuit test mode; and a second signal path switching circuit portion (51) disposed between the memory portion output path (106) and the logic circuit input path (107), which transmits the signal from the memory portion (30) to said memory test output signal path (110) by switching off said logic circuit input path (107) to said logic circuit portion (20) from said logic circuit test pattern (112), when said operation mode is the memory test mode, and also transmits said logic circuit test pattern (112) from said output portion of said logic circuit testing signal memory circuit portion (80) to the logic circuit portion (20) by switching off said memory portion output path (106) from said memory portion (30), when said operation mode is the logic circuit test mode, comprising the steps of: inputting said operation mode signal determining said operation mode of said memory incorporating logic LSI (10) so as to select either one of the memory test and the logic circuit test by switching over the signal path in said first and second signal path switching circuit portions (50, 51); inputting a predetermined test signal from said input and output terminal portion (40); observing the result of the test delivered back to said input and output terminal portion (40); and comparing information obtained by observing said result with predetermined expected information.

Inventors: HATAYAMA KAZUMI, HAYASHI TERUMINE, HATAYAMA, KAZUMI, HAYASHI, TERUMINE
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1988
Main classification: G11C29
IPC codes: H01L21, G06F11, G11C29, G01R31