Abstract:
A design supporting apparatus is disclosed, including: an inputting part; a syntactic analyzing part; and a scanning and searching part. The inputting part inputs functional description data of a register transfer level. The syntactic analyzing part conducts a syntactic analysis for the functional description data and develops a parse tree. The scanning and searching part scans and searches for the parse tree being developed by the syntactic analyzing part and searches for a description representing a comparison operator having multiple bits, the comparison operator being difficult to detect a fault by test data formed by pseudo-random numbers, which are applied from a pseudo-random number generator of a logic built-in self-test.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to design supporting apparatuses being applicable to an analysis system or a design system and easily conducting a test, and more particularly to a design supporting apparatus capable of confirming a description of which a fault in a hardware functional description is difficult to be detected which is independent of an architecture when a large-scale integrated (LSI) circuit is tested by a function of a logic built-in self-test. 
   2. Description of the Related Art 
   For example, a conventional technology of a built-in self-test method (hereinafter, called logic BIST) of a scan-base using a random number for test data is disclosed in a Japanese Laid-open Patent Application No. 5-241882 and a Japanese Patent No. 2711492. Moreover, for example, a checking method for a functional description of a register transfer level is disclosed in Japanese Laid-open Patent Applications No. 11-85828, No. 2000-215225, and No 6-259496. 
   First, the Japanese Laid-open Patent Application No. 5-241882 describes advantages and disadvantages of a BIST circuit design having the function of the built-in self-test in an architecture. As the advantages, since a manufacturer is not required to cover time and cost necessary to embed a special test device in order to check a function and an operation of a circuit under test, test efficiency is improved. In addition, as the disadvantages, since it is required to assign a physical area within an IC (Integrated Circuit), an area for regular functional components is required to be smaller. 
   A circuit in the Japanese Laid-open Patent Application No. 5-241882 functions as a built-in self-test circuit (BIST) to test an operation of a circuit under test by generating a test vector and accumulating signals being output from the circuit under test in response to a test vector. A linear feedback shift register (LFSR) includes a first input being coupled to receive a signal output from the circuit under test, and an output to send a test vector to the circuit under test. 
   Next, the Japanese Patent No. 2711492 describes a distributed built-in self-test circuit for conducting a built-in self-test of a chip in a diagnostic test of an LSI design and a quality test at an LSI production, and more particularly to a pattern compressing device for the built-in self-test. That is, for the built-in self-test with respect to the LSI, it is required to arrange a pattern compressor for each of various functional blocks. Accordingly, because hardware of the built-in self-test is additionally arranged, a chip area is increased and a yield of the LSI is degraded. Therefore, an amount of hardware is required to be reduced as much as possible. As a spatial compressor built-in each functional block, various compressors having different configurations such as a compressor using a multiple input linear feedback shift register, a compressor using an exclusive OR, and a like are combined in sequence based on a smaller amount of hardware. 
   For example, the technologies described in the Japanese Laid-open Patent Applications No. 11-85828 and No. 6-259496 are related to a supporting apparatus to improve a test quality by a test bench that is created by a user, which warns a state coverage and an inactive state of a sequential circuit from a simulation result using the test bench created by the user. 
   Moreover, the Japanese Laid-open Patent Application No. 2000-215225 discloses a technology to examine data propagation from an input to an output based on a simulation result by a test bench created by a user, and to verify a test simplification. 
   Since test data are pseudo-random numbers in the logic BIST, there are cases in which a sufficient fault detection ratio cannot be obtained. In particular, a comparison operator including multiple bits is a circuit (random resistant) in which a fault detection using a pseudo-random number is not easily conducted. Regarding a circuit having an encoder and a conditional branch process being nested, if test data are pseudo-random numbers, a bias occurs after a conditional branch. As a result, there are circuits which remain without being tested. 
   Conventionally, in response to these problems, a technology is disclosed in U.S. Pat. No. 6,070,261 to insert a test circuit at a place where a controllability and an observability in a net list of gate levels are not good. 
   However, in this technology, because of the test circuit being inserted, a circuit function, especially, speed is degraded. In addition, in a case of a large-scale circuit, an execution time becomes longer in an analysis tool for the controllability and the observability. 
   In order to solve the above-described problems, for example, a description being difficult to detect a fault by the logic BIST is extracted at a register transfer level (hereinafter, called RTL), and a test circuit description is additionally described to the description being extracted. A net list of the gate level, in which a countermeasure is taken for the above-described problems, can be obtained. 
   However, it is required to know a description corresponding to a random resistance in the RTL beforehand. 
   Furthermore, in other than the test, an equivalence checking tool is not used for a multiplier having more than 32 bits in an equivalence checking process. Regarding the logic synthesis, if the multiplier is a large-scale circuit, the execution time becomes longer. In response to this problem, it is required to divide the description. In this case, it is needed to know where a problem is in the RTL beforehand. 
   SUMMARY OF THE INVENTION 
   It is a general object of the present invention to provide a design supporting apparatus in which the above-mentioned problems are eliminated. 
   A more specific object of the present invention is to provide the design supporting apparatus which improves a test quality in that test data are random numbers in a test method of a scan base, and can specify and extract a portion degrading the test quality, statically without using a simulator. 
   The above objects of the present invention are achieved by a design supporting apparatus, including: an inputting part inputting functional description data of a register transfer level; a syntactic analyzing part conducting a syntactic analysis for the functional description data and developing a parse tree; and a scanning and searching part scanning and searching for the parse tree being developed by the syntactic analyzing part and searching for a description representing a comparison operator having multiple bits, the comparison operator being difficult to detect a fault by test data formed by pseudo-random numbers, which are applied from a pseudo-random number generator of a logic built-in self-test. 
   Moreover, the above objects of the present invention are achieved by a design supporting apparatus, including: an inputting part inputting functional description data of a register transfer level; a syntactic analyzing part conducting a syntactic analysis of the functional description data and developing a parse tree; a knowledge-based library in that the parse tree being developed by the syntactic analyzing part is possible to be scanned and searched for and description forms to be searched is stored in a rule form; and a searching part searching a relevant description form by referring to the knowledge-based library. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, embodiments of the present invention will be described with reference to the accompanying drawings. 
       FIG. 1  is a diagram showing a hardware configuration of a design supporting apparatus according to a first embodiment of the present invention; 
       FIG. 2A  is a diagram showing an example of the functional description data of the RTL according to the first embodiment of the present invention,  FIG. 2B  is a diagram showing an example of the parse tree that is developed in the storage unit from a description of the RTL by the syntactic analysis according to the first embodiment of the present invention, and  FIG. 2C  is a diagram showing information which is stored in a structure form for each node of the parse tree according to the first embodiment of the present invention; 
       FIG. 3  is a diagram for explaining a state of the design supporting apparatus according to the first embodiment of the present invention; 
       FIG. 4A  and  FIG. 4B  are diagrams illustrating the parse tree in which a process flow description is developed, according to the first embodiment of the present invention; 
       FIG. 5  is a flowchart for explaining a series of processes for searching a comparison operator description having more than 12 bits as the searching process according to the first embodiment of the present invention; 
       FIG. 6  is a diagram showing an example of a description in a program form of the C programming language, according to the first embodiment of the present invention; 
       FIG. 7  is a diagram illustrating a list structure possible to scan by the “next” which refers to a pointer, according to the first embodiment of the present invention; 
       FIG. 8  is a diagram showing an example of a description for searching for more than three branches after a conditional branch of “If-Else”, according to the variation of the first embodiment of the present invention; 
       FIG. 9  is a diagram showing a configuration of a design supporting apparatus according to a second embodiment of the present invention; 
       FIG. 10  is a diagram showing a rule for searching for a comparison operator having more than 12 bits as an example of the knowledge-based library in  FIG. 9 , according to the second embodiment of the present invention; and 
       FIG. 11  is a diagram illustrating assignments of an identifier concerning a type of the operator, according to the second embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the following, embodiments of the present invention will be described with reference to the accompanying drawings. 
   First Embodiment 
     FIG. 1  is a diagram showing a hardware configuration of a design supporting apparatus according to a first embodiment of the present invention. 
   In  FIG. 1 , a storage unit  101  is a memory or a hard disk to store functional description data of a resister transfer level (RTL) and a program realizing each of processing parts of the design supporting apparatus  100 . A CPU (Computer Processing Unit)  102  controls the entire design supporting apparatus  100 . An input unit  103  is a keyboard or a mouse to input and edit a hardware functional description being independent of an architecture and to interactively input an executive instruction of the program of each of processing parts in the design supporting apparatus  100  according to the present invention. 
   A display unit  104  is a CRT (Cathode Ray Tube) to display the hardware functional description being independent of the architecture and display an execution progress and an execution result of the program of each of processing parts according to the present invention. A system bus  105  is an interface (I/F) for each of units  101 ,  102 ,  103 , and  104 . 
   After the CPU  102  conducts a syntactic analysis with respect to the functional description data of the RTL, a parse tree is developed and stored in the storage unit  101  such as the memory or the hard disk. 
   The functional description data of the RTL and the parse tree will be described with  FIG. 2A ,  FIG. 2B , and  FIG. 2C . 
     FIG. 2A  is a diagram showing an example of the functional description data of the RTL according to the first embodiment of the present invention,  FIG. 2B  is a diagram showing an example of the parse tree that is developed in the storage unit from a description of the RTL by the syntactic analysis according to the first embodiment of the present invention, and  FIG. 2C  is a diagram showing information which is stored in a structure form for each node of the parse tree according to the first embodiment of the present invention. 
   Each node of the parse tree stores an operand and an operator of a variable. The operand corresponds to a register or a net. The operator corresponds to a type of an operation such as an addition, a subtraction, a multiplication, a comparison, or a like. In  FIG. 2B , a node denoting “L” is a top node of the parse tree concerning a left side of an arithmetic expression in description data and a node denoting “R” is a top node of the parse tree concerning a right side of an arithmetic expression in the description data. 
   In a structure in  FIG. 2C , for example, “FILE NAME” is an array of a char type of C programming language and stores a file name of the functional description data of the RTL. “LINE NUMBER” stores a line number in an integer type. “TYPE” stores an identifier such as a type of the operator, a type of the register, a type of the net, a type of a port, or the like. 
   In  FIG. 11 , a table ( 1 ) shows an example of an assignment of the identifier concerning the type of the operator. 
   In the table ( 1 ) in  FIG. 11 , “SubOp” represents “−” (subtraction) operation, “DivOp” represents “/” (division) operation, “AddOp” represents “=” (addition) operation, and “MultOp” represents “*” (multiplication) operation. In a case in that the type of the node is the register, the net, or the port, information concerning a bit width is stored in the structure in  FIG. 2C . 
   In a case in that there are a plurality of operational expressions and conditional branch processes in the functional description data of the RTL to input, the parse tree is created for each operation, and a top node of each parse tree is stored in a list form or a hash table form on the memory. In this case, the parse trees can be browsed and referred to by scanning the memory. 
     FIG. 3  is a diagram for explaining a state of the design supporting apparatus according to the first embodiment of the present invention. 
   That is,  FIG. 3  shows states of components, the functional description data of the RTL, and the parse tree being developed in the storage unit  101  such as the memory or the hard disk by the syntactic analysis, and a state of storing the parse tree to a table so as to be possible to scan, search, and browse the parse tree. 
   A functional description data  301  is a functional description data of the RTL to input, a syntactic analyzing part  302  is a processing part for conducing the syntactic analysis according to the present invention, a detecting part  303  is a processing part for detecting the parse tree, a CRT  304  displays a detection result, a table  305  is a table provided by the detecting part  303  to be possible to scan, search, and brows the parse tree, the parse tree  306  is a parse tree being developed by conducting the syntactic analysis for the operation expression and the conditional branch process in the functional description data  301 , a pointer  307  is a pointer possible to refer to the parse tree  306  from the table  305 , and a pointer  308  is pointer possible to refer to the table  305  from the detecting part  303 . The table  305  may be configured as a list structure. 
   A process flow in the functional description data  301  of the RTL is also stored in a form of the parse tree  306 . 
   The process flow corresponds to a case statement of a Verilog HDL (Hardware Description Language) or a conditional branch description in an if_els form 
     FIG. 4A  and  FIG. 4B  are diagrams illustrating the parse tree in which a process flow description is developed, according to the first embodiment of the present invention. 
   In  FIG. 4A , an example of the if_els form is shown. In  FIG. 4B , “C” denotes a conditional expression, that is, a node for storing a pointer to refer to the parse tree concerning the conditional expression, and the conditional expression configures the parse tree. In  FIG. 4B , “y” denotes a node for storing a pointer to refer to the parse tree concerning an operation that is executed when a condition is true and “n” denotes a node for storing a pointer to refer to the parse tree concerning an operation that is executed when a condition is false. Each operation to be executed configures the parse tree. These parse trees are stored in the list form or the hash table form and can be scanned for reference and to browse. 
   In the present invention, in the above-described configuration, it is possible to scan, browse, and refer to the parse tree being developed in the storage unit  101  such as the memory or the hard disk. Accordingly, description forms described in the functional description data of the RTL can be confirmed and analyzed. According to a passed technical report, the comparison operator having multiple bits is a circuit (random resistant) being difficult to detect a fault by a pseudo-random number. Regarding a circuit having the encoder and the nested conditional branch process, in a case in which the test data are pseudo-random numbers, a bias occurs after the conditional branch. As a result, there are circuits which remain without being tested. 
   However, in the first embodiment, by scanning, browsing, and referring to the parse tree, for example, a node for the comparison operator is searched for and a register as an operand and the bit width of the net is further referred to. If a result shows a comparison operator having more than 12 bits, the file name and the line number of the functional description data  301  of the RTL are displayed at the CRT  304 . 
     FIG. 5  is a flowchart for explaining a series of processes for searching a comparison operator description having more than 12 bits as the searching process according to the first embodiment of the present invention.  FIG. 6  is a diagram showing an example of a description in a program form of the C programming language, according to the first embodiment of the present invention. 
   When a search begins, each pointer of nodes being stored in a table or a list is scanned from a start node (step  501 ), and a comparison operator having a 12-bit width with respect to a node being referred to is searched. If a relevant node is found, the file name and the line number of the relevant node are displayed at the CRT (step  502 ). When the table or the list is scanned until the end thereof (step  503 ), the scanning process is terminated. 
   Lines  1 - 7  in  FIG. 6  shows a structure for string information which each node in the node tree holds. “FileName” and “LineNumber” store a file name and a line number of the functional description data of the RTL, “Type” stores an identifier for distinguish types of the operation, the register, the port, and the net, “OpeType” stores an identifier of the operator, “next” stores a pointer of a next node so that it is possible to scan the parse tree in the table of the list structure, and “sub” stores a set of pointers to refer to a node of a sub tree from another sub tree in the parse tree. 
   Lines  32 - 34  in  FIG. 6  are for a looping process including the steps  501  and  502  in  FIG. 5  to scan the parse tree in the table or the list. 
   A “search” function described in lines  10 - 26  in  FIG. 6  conducts a process of the step S 502  in  FIG. 5 . An argument “parent” receives a top node of the parse tree, and the parse tree is searched by a while statement in lines  15 - 25 . A “get_node” function in line  15  is used to choose one node from the set of sub trees, and all sub trees are scanned by awhile process. A process described in lines  17 - 20  displays the file name and the line number if the node is an operator and the comparison operator, and the bit width of the node is more than 12 bits. “EqOp”, “GtOp”, and “LtOp” in line  17  are identifiers of the comparison operators: equal, greater than, and less than. A “get_operand_bit_width” function in line  18  returns the bit width of the register, the port, or the net of the operand by referring to the sub tree of the node “v”. In addition, a “shpw” function displays the file name and the line number for a description corresponding to the node at the CRT. 
   In this search process, the “search” function is recursively called, so that the parse tree is searched until the end node. 
   A table ( 3 ) in  FIG. 11  shows an identifier for distinguishing a type of the operator, the register, the port, and the net, which is stored in “Type” described above. 
   “Operator” in the table ( 3 ) shows that the node is the operator, and “Variable” shows any one of the register, the port, and the net. In addition, “ifElse” shows that the node is a “If-Else” type and “Case” shows that the node is a conditional branch of a case branch type. 
     FIG. 7  is a diagram illustrating a list structure possible to scan by the “next” which refers to a pointer, according to the first embodiment of the present invention 
   The set of sub trees is of storing the nodes of the sub tress in the list structure. 
   [Variation of First Embodiment] 
   In the first embodiment, the multiplication operator is conducted by 12 bits. In a variation of the first embodiment, a case of searching for the multiplication operator being conducted by more than 32 bits will be described. In this case, “MultOp” is set to compare with “OpType” in line  17  in  FIG. 6  and a bit width comparison in line  18  in  FIG. 6  is set to “32”. 
     FIG. 8  is a diagram showing an example of a description for searching for more than three branches after a conditional branch of “If-Else”, according to the variation of the first embodiment of the present invention. 
   Instead of the “search” function, “search_if_else” function is conducted. In line  10 , it is checked whether or not the node is a node to conduct the conditional branch of “If-Else”. When the node conducts the conditional branch of “If-Else”, a looping process in lines  12 - 20  searches for a tree of “If_Else” and counts a depth of the parse tree by incrementing “i” by one. As a result, when “i” is more than three or equal to three, the file name and the line number are displayed at the CRT. 
   Second Embodiment 
     FIG. 9  is a diagram showing a configuration of a design supporting apparatus according to a second embodiment of the present invention. 
   In  FIG. 9 , the functional description data of the RTL being input and the parse tree being stored in the memory or the hard disk are illustrated. In  FIG. 9 , a knowledge-based library  909  is configured by a rule of “If_Then”. A searching part  903  conducts a searching process in accordance with the rule of the knowledge-based library  909 . 
   In  FIG. 9 , a functional description data  901  is a functional description data of the RTL to input, a syntactic analyzing part  902  is a processing part for conducing the syntactic analysis according to the present invention, a CRT  904  displays a detection result, a table  905  is a table provided by the searching part  903  to be possible to scan, search, and browse the parse tree, the parse tree  906  is a parse tree being developed by conducting the syntactic analysis for the operation expression and the conditional branch process in the functional description data  901 , a pointer  907  is a pointer possible to refer to the parse tree  906  from the table  905 , and a pointer  908  is a pointer possible to refer to the table  905  from the searching part  903 . The table  905  may be configured as a list structure. 
     FIG. 10  is a diagram showing a rule for searching for a comparison operator having more than 12 bits as an example of the knowledge-based library in  FIG. 9 . 
   A description  1001  indicates that an operator to search is “EqOp”, and a description.  1002  indicates that the bit width is greater than and equal to 12 bits. When the searching part  903  refers to this, the searching part  903  conducts “EqOp” of the description  1001  as a condition of an operator matching in line  17  in  FIG. 6 , and further conducts a condition showing more than 12 bits in the description  1002  as a comparison value of the 12-bit width in line  18  in  FIG. 6 . 
   A description  1003  in  FIG. 10  shows a rule description ruling the multiplication being more than 32 bits. 
   As described above, in the present invention, since the RTL is developed as the parse tree in the memory or the hard disk, it is possible to scan and search for an operation and a condition description. Accordingly, it is possible to search for each node of a large-scale comparison operator occurring a fault at a test and each node of a large-scale multiplication circuit occurring a fault at the test when the equivalence checking or the logic synthesis is conducted, and it is possible to warn a relevant description portion by the file name and the line number. As a result, it is possible to warn a modification concerning a description of the RTL, which occurs a fault at the test, the equivalence checking, and the logic synthesis, and it is possible to contend with the modification at an earlier stage of the design. 
   In addition, since description forms to be searched is maintained as the knowledge-based library, it is possible to delete a rule concerning a description form, which has been already overcome, accompanying with an increase of an amount of the description forms being maintained. Therefore, a check specifying any one of the test, the equivalence checking, and the logic synthesis can be realized. 
   In the design supporting apparatus according to the present invention, it is possible to test whether or not a RTL description style, which is experientially known as random resistant, is written in a RTL created by a user. If the RTL description style is written, it is possible to warn this result so as to support a design work of a test simplification for the logic BIST. 
   Moreover, by this warning, the user (LSI designer or circuit designer) can easily recognize a description portion being warned Thus, the user can take a step of a TPI (Test Protocol Input) with respect to a relative block or properly improve a timing by a logic compression after the TPI. Accordingly, it is possible to suppress a length of a development term. 
   In other than the test, it is possible to prompt the user (LSI designer or circuit designer) by confirming and warning the large-scale multiplier, which cause a problem by the equivalence checking or the logic synthesis. 
   Furthermore, in the design supporting apparatus according to the present invention, it is possible for the user (LSI designer or circuit designer) to add and modify description forms as a knowledge base, and then to detect a desired description form. As a result, it is possible to add a new description form, which occurs a problem by a tool such as the test, the equivalence checking, the logic synthesis, or the like, and it is possible to delete a rule concerning a description form that has been already overcome. Therefore, a check specifying any one of the test, the equivalence checking, and the logic synthesis can be realized. 
   The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention. 
   The present application is based on the Japanese Priority Application No. 2003-298291 filed on Aug. 22, 2003, the entire contents of which are hereby incorporated by reference.