Patent Publication Number: US-2013245975-A1

Title: Drawing device, drawing method, and computer-readable recording medium

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-062772, filed on Mar. 19, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to a drawing device, a drawing method, and drawing program. 
     BACKGROUND 
     In an electric circuit that is disposed on a laminated circuit board such as a printed circuit board, in a case where power is supplied from a power supplying component such as a power supplying pin to an integrated circuit, a voltage drop occurs due to the resistance of a conductive body such as a plane or a via. Since a voltage of a predetermined level or higher is used so as to operate an integrated circuit, for example, a large scale integration (LSI), the voltage drop is calculated through an analysis or the like, and it is verified whether or not a voltage applied to the LSI satisfies a voltage value used for operating the LSI. This verification may be performed by a person. Thus, there is a technology for processing the appearance of the voltage drop that is calculated through an analysis or the like into a form that can be perceived by a person and displaying the processed appearance of the voltage drop. 
     For example, there is a technology in which an image, in which voltages calculated by an analysis are represented in colors corresponding to the voltages, is two-dimensionally or three-dimensionally displayed as the appearance of a voltage drop when seen in the Z axis direction in a laminated circuit board. In addition, there is a technology in which an image represented by colors or thicknesses of lines corresponding to the amounts of currents is two-dimensionally or three-dimensionally displayed as the appearance of a flowing current when seen in the Z axis direction in a laminated circuit board.
     Patent Document 1: Japanese Laid-open Patent Publication No. 2002-203001   Patent Document 2: Japanese Laid-open Patent Publication No. 2004-199279   

     However, according to the conventional technologies described above, there is a problem in that it is difficult to perceive the appearance of a voltage drop in the laminated circuit board in an easy manner. 
     For example, according to the technology in which an image, in which voltages calculated by an analysis are represented in colors corresponding to the voltages, is two-dimensionally displayed as the appearance of a voltage drop when seen in the Z axis direction in a laminated circuit board, the voltage drop in a plane of a specific layer is two-dimensionally displayed. Accordingly, it is difficult to perceive the appearance of a voltage drop in the entire laminated circuit board from the two-dimensional image. In addition, since the plane and a via intersect each other, it is difficult to perceive a voltage drop in the Z axis direction, that is, the direction of the via from the display of the appearance of a voltage drop in the plane of the specific layer. 
     In addition, according to the technology in which an image, in which voltages calculated by an analysis are represented in colors corresponding to the voltages, is three-dimensionally displayed, the size of a via that is displayed is smaller than the size of the plane. In addition, since there is an overlap between displays of the via and the plane, it is difficult to perceive the via that is relatively small unless it is displayed in an enlarged scale. According to the technology in which the appearance of a voltage effect is three-dimensionally displayed, in order to perceive a voltage drop in the entire laminated circuit board, a movement of a portion to be displayed and the scaling of a display are repeatedly performed. Accordingly, it is difficult to perceive the appearance of the voltage drop in the entire laminated circuit board in an easy manner. 
     SUMMARY 
     According to an aspect of an embodiment, a drawing device includes a memory and a processor coupled to the memory. The processor executes a process including measuring voltages of planes of layers in a laminated circuit board and drawing the voltages of the planes that are measured on a graph having a voltage set on one axis and having a layer set on the other axis. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram that illustrates an example of the functional configuration of a drawing device according to a first embodiment; 
         FIG. 2  is a diagram that illustrates an example of the data structure of first CAD data; 
         FIG. 3  is a diagram that illustrates an example of the data structure of second CAD data; 
         FIG. 4  is a schematic diagram of a laminated circuit board; 
         FIG. 5  is a diagram that illustrates an example of the data structure of a measurement point table; 
         FIG. 6  is a diagram that illustrates an example of the data structure of a connection table; 
         FIG. 7  is a diagram that illustrates an example of the process of recording various kinds of information in the measurement point table; 
         FIG. 8  is a diagram that illustrates an example of the process of recording various kinds of information in the measurement point table; 
         FIG. 9  is a diagram that illustrates an example of the process for recording various kinds of information in the connection table; 
         FIG. 10  is a diagram that illustrates an example of the process for recording various kinds of information in the connection table; 
         FIG. 11  is a diagram that illustrates an example of the measurement point table in which various kinds of information are recorded by a recording unit; 
         FIG. 12  is a diagram that illustrates an example of the X axis and the Y axis that are drawn by a drawing unit; 
         FIG. 13  is a diagram that illustrates an example of a segment formed by a minimal voltage and a maximal voltage of each plane that is drawn by the drawing unit; 
         FIG. 14  is a diagram that illustrates an example of a segment representing a voltage drop of a via that is drawn by the drawing unit; 
         FIG. 15  is a diagram that illustrates the correspondence relation between a generated graph and a plane, a via, a power supplying pin, and a power consuming pin of the laminated circuit board; 
         FIG. 16  is a flowchart that illustrates the sequence of a drawing process according to the first embodiment; 
         FIG. 17  is a flowchart that illustrates the sequence of a recording process according to the first embodiment; 
         FIG. 18  is a flowchart that illustrates the sequence of the recording process according to the first embodiment; 
         FIG. 19  is a flowchart that illustrates the sequence of a measurement process according to the first embodiment; 
         FIG. 20  is a flowchart that illustrates the sequence of a coordinate-axis drawing process according to the first embodiment; 
         FIG. 21  is a flowchart that illustrates the sequence of a plane voltage drop drawing process according to the first embodiment; 
         FIG. 22  is a flowchart that illustrates the sequence of a via voltage drop drawing process according to the first embodiment; 
         FIG. 23  is a diagram that illustrates an example of the functional configuration of a drawing device according to a second embodiment; 
         FIG. 24  is a diagram that illustrates an example of the data structure of a connection table according to the second embodiment; 
         FIG. 25  is a diagram that illustrates an example of a segment that represents the magnitude of a current flowing through a via that is drawn by a drawing unit; 
         FIG. 26  is a flowchart that illustrates the sequence of a measurement process according to the second embodiment; 
         FIG. 27  is a flowchart that illustrates the sequence of a via voltage drop drawing process according to the second embodiment; 
         FIG. 28  is a schematic diagram of a laminated circuit board in a case where there is a plurality of paths connecting two points in a net and the paths go through planes that are different from each other; 
         FIG. 29  is a diagram that illustrates an example of the functional configuration of a drawing device according to a third embodiment; 
         FIG. 30  is a diagram that illustrates an example of the data structure of a connection table according to the third embodiment; 
         FIG. 31  is a diagram that illustrates an example of a method of generating a sorted table; 
         FIG. 32  is a diagram that illustrates an example of a method of generating a sorted table; 
         FIG. 33  is a diagram that illustrates an example of a connection table; 
         FIG. 34  is a schematic diagram that illustrates some vias and some planes that are represented by the sorted table illustrated in the example represented in  FIG. 32 ; 
         FIG. 35  is a diagram that illustrates an example of the thickness of a segment that is drawn by the drawing unit; 
         FIG. 36  is a diagram that illustrates an example of the thicknesses of segments that are drawn by the drawing unit; 
         FIG. 37  is a flowchart that illustrates the sequence of a plane voltage drop drawing process according to the third embodiment; 
         FIG. 38  is a diagram that illustrates an example of the functional configuration of a drawing device acquired by adding a function of a determination process to the drawing device according to each embodiment; 
         FIG. 39  is a flowchart that illustrates the sequence of a drawing process to which the determination process is added; 
         FIGS. 40A and 40B  are flowcharts that illustrate the sequence of the determination process; and 
         FIG. 41  is a diagram that illustrates a computer that executes drawing program. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Preferred embodiments of the present invention will be explained with reference to accompanying drawings. 
     However, the embodiments are not for the purpose of limiting the technology to be disclosed. In addition, the embodiments can be appropriately combined with each other in a range in which the process contents are not contradictory to each other. 
     [a] First Embodiment 
     Hereinafter, a drawing device according to a first embodiment will be described.  FIG. 1  is a diagram that illustrates an example of the functional configuration of the drawing device according to the first embodiment. 
     Functional Configuration of Drawing Device  10   
     As illustrated in  FIG. 1 , a drawing device  10  includes an input unit  11 , a display unit  12 , a storage unit  13 , and a control unit  14 . 
     The input unit  11  inputs various kinds of information to the control unit  14 . For example, the input unit  11  receives an instruction that is used for performing a drawing process to be described below from a user and inputs the received instruction to the control unit  14 . In addition, the input unit  11  receives various instructions from the user and inputs the received instruction to the control unit  14 . As an example of the device that is used as the input unit  11 , there is a device such as a mouse or a keyboard that receives a user&#39;s operation. 
     The display unit  12  displays various kinds of information. For example, the display unit  12  displays a graph, in which voltages of planes of a laminated circuit board is drawn, having the voltage represented in one axis and the layer represented in the other axis under the control of a display control unit  14   d  to be described below. As an example of a device that is used as the display unit  12 , there is a liquid crystal display. 
     The storage unit  13  stores various kinds of information. For example, the storage unit  13  stores first computer aided design (CAD) data  13   a , second CAD data  13   b , a measurement point table  13   c , a connection table  13   d , and image data  13   e.    
     In the first CAD data  13   a , information is included in which the types of elements such as a via included in the laminated circuit board, a power supplying pin supplying power, and a power consuming pin consuming power, the positions of the elements, and layers to which the elements are connected are associated with each other.  FIG. 2  is a diagram that illustrates an example of the data structure of the first CAD data. In the example represented in  FIG. 2 , the first CAD data  13   a  has an entry in which the type of an element included in the laminated circuit board is registered, an entry in which coordinates representing the position of an element are registered, and an entry in which a layer number that is a number of a layer to which an element is connected is registered. The example represented in  FIG. 2  illustrates that the coordinates representing the position of an element of which the type is the power supplying pin are (90.000, 70.000), and such an element is connected to a layer of a layer number L 1 . In addition, the example represented in  FIG. 2  illustrates that the coordinates representing an element of which the type is the via are (75.000, 70.000), and such an element is connected to layers of layer numbers L 1  and L 2 . Furthermore, the example represented in  FIG. 2  illustrates that the coordinates representing the position of an element of which the type is the power consuming pin are (10.000, 10.000), and such an element is connected to the layer of the layer number L 1 . 
     In the second CAD data  13   b , information is included in which identifiers of planes included in the laminated circuit board, shapes of the planes that are represented by the identifiers, the coordinates of vertexes of the planes that are represented by the identifiers, and layers in which the planes represented by the identifiers are present are associated with each other.  FIG. 3  is a diagram that illustrates an example of the data structure of the second CAD data. In the example represented in  FIG. 3 , the second CAD data  13   b  has an entry in which an identifier of a plane included in the laminated circuit board is registered, an entry in which a type of the shape of a plane represented by the identifier is registered, and an entry in which coordinates of vertexes of the plane represented by the identifier are registered. In addition, in the example represented in  FIG. 3 , the second CAD data  13   b  has an entry in which a layer number of a layer in which the plane represented by the identifier is present is registered. The example represented in  FIG. 3  illustrates a case in which the type of the shape of a plane that is represented by an identifier p 001  is a polygon. In addition, the example represented in  FIG. 3  illustrates a case in which the coordinates of vertexes of the plane represented by the identifier p 001  are (70.000, 65.000), (95.000, 65.000), (95.000, 75.000), and (70.000, 75.000). Furthermore, the example represented in  FIG. 3  illustrates a case in which the layer number of a layer in which the plane represented by the identifier p 001  is present is L 1 . 
     Here, a laminated circuit board that includes vias, a power supplying pin, and a power consuming pin that are represented by the first CAD data  13   a  and planes that are represented by the second CAD data  13   b  will be described.  FIG. 4  is a schematic diagram of the laminated circuit board. The laminated circuit board represented by the example represented in  FIG. 4  includes a power supplying pin  15 , planes  17  that are disposed in layers of layer numbers L 1 , L 2 , and L 3 , vias  16  that connects the planes  17  of each layer, and a power consuming pin  18 . In the laminated circuit board illustrated in the example represented by  FIG. 4 , in a case where power is supplied from the power supplying pin  15  to the power consuming pin  18 , a voltage drop of 0.08 V from the power supplying pin  15  to the power consuming pin  18  occurs. The reason for the occurrence of the voltage drop is the presence of resistance in the vias  16  and the planes  17 . In this embodiment, the drawing device  10  generates image data  13   e  from which the appearance of a voltage drop in the laminated circuit board can be easily perceived. 
     The measurement point table  13   c  includes information that relates to measurement points at which voltages or currents are measured. In the measurement point table  13   c , various kinds of contents are registered by a recording unit  14   a  and a measurement unit  14   b  to be described below.  FIG. 5  is a diagram that illustrates an example of the data structure of the measurement point table. The measurement point table  13   c  illustrated in the example represented in  FIG. 5  has an entry in which an identifier of a measurement point is registered, an entry in which a value of the x coordinate of a measurement point represented by the identifier is registered, an entry in which a value of the y coordinate of the measurement point represented by the identifier is registered, and an entry in which a layer number of a layer to which an element having the measurement point represented by the identifier can be connected. In addition, the measurement point table  13   c  illustrated in the example represented in  FIG. 5  has an entry in which an identifier of a plane that includes the position of the measurement point represented by the identifier on the inside of the area is registered, an entry in which the type of an element having the measurement point represented by the identifier is registered, and an entry in which a voltage value of the measurement point represented by the identifier is registered. 
     A first record of the measurement point table  13   c  represented in  FIG. 5  is a record that represents information relating to a measurement point, at which a voltage or a current is measured, of identifier m 001 . The first record of the measurement point table  13   c  represented in  FIG. 5  represents that the coordinates representing the position of the measurement point of identifier m 001  are (90.000, 70.000), and a layer to which an element having the measurement point of identifier m 001  can be connected is a layer of layer number L 1 . In addition, the first record of the measurement point table  13   c  represented in  FIG. 5  represents that a plane of identifier p 001  includes the position of the measurement point of identifier m 001  inside the area. Furthermore, the first record of the measurement point table  13   c  represented in  FIG. 5  represents that the type of the element having the measurement point of identifier m 001  is a power supplying pin, and a voltage value at the measurement point of identifier m 001  is 1.5. The other records similarly represent contents thereof. 
     The connection table  13   d  includes various kinds of information such as a position of a measurement point that is a point at which a voltage or a current is measured, an identifier of the measurement point, and a type of an element having the measurement point. Various kinds of contents are registered in the connection table  13   d  by a recording unit  14   a  to be described below.  FIG. 6  is a diagram that illustrates an example of the data structure of the connection table. The connection table  13   d  illustrated in the example represented in  FIG. 6  includes: an entry in which a value of the x coordinate of a measurement point represented by an identifier is registered; an entry in which a value of the y coordinate of the measurement point represented by the identifier is registered; and an entry in which a type of an element having the measurement point represented by the identifier is registered. In addition, the connection table  13   d  illustrated in the example represented in  FIG. 6  includes an entry in which the type of an element including a measurement point that is represented by the identifier is registered. 
     A first record of the connection table  13   d  represented in  FIG. 6  is a record that represents information relating to a measurement point, at which a voltage or a current is measured, of identifier m 001 . The first record of the connection table  13   d  represented in  FIG. 6  represents that the coordinates representing the position of the measurement point of identifier m 001  are (90.000, 70.000), and the type of an element having a measurement point of identifier m 001  is the power supplying pin. The other records similarly represent contents thereof. 
     The image data  13   e  is generated by a drawing unit  14   c  to be described below. In the image data  13   e , data of a graph in which voltages of planes of the laminated circuit board are drawn, having the voltage as one axis and the layer as the other axis is included. An image that is represented by the image data  13   e  will be described below. 
     The storage unit  13 , for example, is a semiconductor memory device such as a flash memory or a storage device such as a hard disk or an optical disc. The storage unit  13  is not limited to the storage device of a type described above and may be a random access memory (RAM) or a read only memory (ROM). 
     The control unit  14  includes an internal memory used for storing a program that defines various processing sequences or control data and performs various processes based on these. As illustrated in  FIG. 1 , the control unit  14  includes a recording unit  14   a , a measurement unit  14   b , a drawing unit  14   c , and a display control unit  14   d.    
     The recording unit  14   a  records various kinds of information. For example, the recording unit  14   a  records various kinds of information in the measurement point table  13   c  and the connection table  13   d . A method of recording information in the measurement point table  13   c  and the connection table  13   d  using the recording unit  14   a  will now be described with reference to a specific example. 
     The recording unit  14   a , first, acquires the first CAD data  13   a  and the second CAD data  13   b  from the storage unit  13 . Then, the recording unit  14   a  determines whether or not there is an element, which has not been selected, out of a plurality of elements represented by the first CAD data  13   a . Subsequently, in a case where there is an element that has not been selected, the recording unit  14   a  selects one element, which has not been selected, out of a plurality of elements represented by the first CAD data  13   a . Thereafter, the recording unit  14   a  stores the type of the selected element in parameter t. thereby updating the registered content of parameter t. In addition, the recording unit  14   a  stores the coordinates of a position at which the selected element is located in parameter (x, y), thereby updating the registered content of parameter (x, y). Thereafter, the recording unit  14   a  sorts the layers of planes to which the selected element can be connected in the ascending order. 
     For example, the recording unit  14   a  acquires the first CAD data illustrated in  FIG. 2 . Then, in a case where the via illustrated in the example represented in  FIG. 2  is selected as an element that has not been selected, the recording unit  14   a  stores “via” in parameter t and stores (75.000, 70.000) in parameter (x, y). Then, the recording unit  14   a  sorts layers of planes to which the selected via can be connected, in other words, layers of layer numbers L 1  and L 2  in the ascending order. 
     Then, the recording unit  14   a  determines whether or not there is a layer z that has not been selected out of the layers that are sorted in the ascending order. In a case where there is no layer z that has not been selected, the recording unit  14   a  performs the above-described process of determining whether or not there is an element that has not been selected out of a plurality of elements represented by the first CAD data  13   a  again and, as described above, performs the subsequent processes after the process of determining whether or not there is an element that has not been selected again. 
     On the other hand, in a case where there is a layer z that has not been selected, the recording unit  14   a  selects one layer that is a layer z that has not been selected and is a layer z that has a least layer number out of the sorted layers. Then, the recording unit  14   a  determines whether or not there is a plane p that has not been selected out of planes that are present in the selected layer z by referring to the second CAD data  13   b . In a case where there is no plane p that has not been selected, the recording unit  14   a  performs the above-described process of determining whether or not there is a layer z that has not been selected again and, as described above, performs the subsequent processes after the process of determining whether or not there is a layer z that has not been selected again. 
     On the other hand, in a case where there is a plane p that has not been selected, the recording unit  14   a  selects one plane p that has not been selected out of planes that are present in the selected layer z. Then, the recording unit  14   a  determines whether or not the coordinates stored in parameter (x, y) are present inside the area of the selected plane p by referring to the second CAD data. In a case where the coordinates are not present on the inside, the recording unit  14   a  performs the above-described process of determining whether or not there is a plane p that has not been selected out of planes that are present in the selected layer z again and, as described above, performs the subsequent processes after the process of determining whether or not there is a plane p that has not been selected again. 
     On the other hand, in a case where the coordinates stored in parameter (x, y) are present inside the area of the selected plane p, the recording unit  14   a  performs a process as follows. That is, the recording unit  14   a  stores the value of the x coordinate and the value of the y coordinate of coordinates stored in parameter (x, y), a layer number of the selected layer z, an identifier of the selected plane p, and the type of the element stored in parameter t in association with the identifier m of the measurement point in the measurement point table  13   c.    
     A specific example of recording various kinds of information in the measurement point table  13   c  will be described.  FIGS. 7 and 8  are diagrams that illustrate examples of the process of recording various kinds of information in the measurement point table. For example, a case will be described in which coordinates stored in parameter (x, y) are (90.000, 70.000), the layer number of a selected layer z is L 1 , the identifier of a selected plane p is p 001 , and the type of an element that is stored in parameter t is the power supplying pin. In such a case, when the identifier of a measurement point is m 001 , the recording unit  14   a , as illustrated in the example represented in  FIG. 7 , records m 001  in the entry in which an identifier of a measurement point is registered and records 90.000 in the entry in which the value of the x coordinate of the measurement point represented by the identifier is registered. In addition, the recording unit  14   a , as illustrated in the example represented in  FIG. 7 , records 70.000 in the entry in which a y coordinate of the measurement point represented by the identifier is registered and records L 1  in the entry in which a layer number of a layer to which an element having the measurement point represented by the identifier can be connected is registered. Furthermore, the recording unit  14   a , as illustrated in the example represented in  FIG. 7 , records p 001  in the entry in which an identifier of a plane that includes the position of the measurement point represented by the identifier on the inside of the area is registered and records the power supplying pin in the entry in which the type of an element having the measurement point represented by the identifier is registered. 
     In addition, a case will be described in which coordinates stored in parameter (x, y) are (75.000, 70.000), the layer number of a selected layer z is L 1 , the identifier of a selected plane p is p 001 , and the type of an element that is stored in parameter t is the via. In such a case, when the identifier of a measurement point is m 002 , the recording unit  14   a , as illustrated in the example represented in  FIG. 8 , records m 002  in the entry in which an identifier of a measurement point is registered and records 75.000 in the entry in which the value of the x coordinate of the measurement point represented by the identifier is registered. In addition, the recording unit  14   a , as illustrated in the example represented in  FIG. 8 , records 70.000 in the entry in which a y coordinate of the measurement point represented by the identifier is registered and records L 1  in the entry in which a layer number of a layer to which an element having the measurement point represented by the identifier can be connected is registered. Furthermore, the recording unit  14   a , as illustrated in the example represented in  FIG. 8 , records p 001  in the entry in which an identifier of a plane that includes the position of a measurement point represented by the identifier on the inside of the area is registered and records the via in the entry in which the type of an element having the measurement point represented by the identifier is registered. 
     Furthermore, a case will be described in which coordinates stored in parameter (x, y) are (75.000, 70.000), the layer number of a selected layer z is L 2 , the identifier of a selected plane p is p 002 , and the type of an element that is stored in parameter t is the via. In such a case, when the identifier of a measurement point is m 003 , the recording unit  14   a , as illustrated in the example represented in  FIG. 8 , records m 003  in the entry in which an identifier of a measurement point is registered and records 75.000 in the entry in which the value of the x coordinate of the measurement point represented by the identifier is registered. In addition, the recording unit  14   a , as illustrated in the example represented in  FIG. 8 , records 70.000 in the entry in which a y coordinate of the measurement point represented by the identifier is registered and records L 2  in the entry in which a layer number of a layer to which an element having the measurement point represented by the identifier can be connected is registered. Furthermore, the recording unit  14   a , as illustrated in the example represented in  FIG. 8 , records p 002  in the entry in which an identifier of a plane that includes the position of a measurement point represented by the identifier on the inside of the area is registered and records the via in the entry in which the type of an element having the measurement point represented by the identifier is registered. 
     Then, the recording unit  14   a  determines whether or not the type of the element that is stored in parameter t is the via. In a case where the type is not the via, the recording unit  14   a  records a value of the x coordinate and a value of the y coordinate of coordinates stored in parameter (x, y) and the type of an element that is stored in parameter t in association with the identifier m of the measurement point in the connection table  13   d . Then, the recording unit  14   a  performs the above-described process of determining whether or not there is a plane p that has not been selected out of planes present in the selected layer z again and, as described above, performs subsequent processes after the process of determining whether or not there is a plane p that has not been selected again. 
     On the other hand, in a case where the type of the element that is stored in parameter t is the via, the recording unit  14   a  determines whether or not the selected layer z is an uppermost layer of sorted layers. In a case where the selected layer is the uppermost layer, the recording unit  14   a  stores an identifier m of the measurement point in parameter m′, thereby updating the registered content of parameter m′. Then, the recording unit  14   a  performs the above-described process of determining whether or not there is a plane p that has not been selected out of the planes present in the selected layer z again and, as described above, performs the subsequent processes after the process of determining whether or not there is a plane p that has not been selected again. 
     Here, in a case where the selected layer z is not the uppermost layer of the sorted layers, the recording unit  14   a  performs a process as follows. That is, the recording unit  14   a  records a value of the x coordinate and a value of the y coordinate of coordinates stored in parameter (x, y) and the type of an element that is stored in parameter t in association with the identifier m of the measurement point and the identifier of a measurement point that is stored in parameter m′ in the connection table  13   d . Then, the recording unit  14   a  stores the identifier m of the measurement point in parameter m′, thereby updating the registered content of parameter m′. Thereafter, the recording unit  14   a  performs the above-described process of determining whether or not there is a plane p that has not been selected out of the planes present in the selected layer z again and, as described above, performs the subsequent processes after the process of determining whether or not there is a plane p that has not been selected again. 
     A specific example of recording various kinds of information in the connection table  13   d  will be described.  FIGS. 9 and 10  are diagrams that illustrate examples of the process of recording various kinds of information in the connection table. For example, a case will be described in which coordinates stored in parameter (x, y) are (90.000, 70.000), and the type of an element that is stored in parameter t is the power supplying pin. In such a case, when the identifier of a measurement point is m 001 , the recording unit  14   a , as illustrated in the example represented in  FIG. 9 , records 90.000 in the entry in which the value of the x coordinate of the measurement point represented by the identifier is registered and records 70.000 in the entry in which the value of the y coordinate of the measurement point represented by the identifier is registered. In addition, the recording unit  14   a , as illustrated in the example represented in  FIG. 9 , records m 001  in the entry in which an identifier of the measurement point is registered and records the power supplying pin in the entry in which the type of an element having the measurement point represented by the identifier is registered. 
     In addition, a case will be described in which coordinates stored in parameter (x, y) are (75.000, 70.000), the type of an element that is stored in parameter t is the via, and the identifier of a measurement point that is stored in parameter m′ is m 002 . In such a case, when the identifier of the measurement point is m 003 , the recording unit  14   a , as illustrated in the example represented in  FIG. 10 , records 75.000 in the entry in which the value of the x coordinate of a measurement point that is represented by the identifier is registered and records 70.000 in the entry in which the value of the y coordinate of the measurement point that is represented by the identifier is registered. In addition, the recording unit  14   a , as illustrated in the example represented in  FIG. 10 , records m 002  and m 003  in the entry in which an identifier of a measurement point is registered and registers the via in the entry in which the type of an element having the measurement point represented by the identifier is registered. Here, the measurement point represented by the identifier that is stored in parameter m′ and the measurement point represented by an identifier m that is newly assigned are measurement points included in the same via. In such a case, the measurement point represented by the identifier stored in parameter m′ is disposed in a layer that is located upper than a layer in which the measurement point represented by the identifier m that is newly assigned is disposed. 
     The recording unit  14   a  repeatedly performs the above-described process until there is no element that has not been selected.  FIG. 11  is a diagram that illustrates an example of the measurement point table in which various kinds of information is recorded by the recording unit. By performing the above-described process until there is no element that has not been selected, repeatedly, the recording unit  14   a  generates the measurement point table  13   c  as illustrated in the example represented in  FIG. 11  and the connection table  13   d  as illustrated in the previous example represented in  FIG. 6 . 
     The measurement unit  14   b  measures a voltage of a plane of each layer and voltages of via in the laminated circuit board. A specific example will be described. First, the measurement unit  14   b  acquires the measurement point table  13   c  from the storage unit  13  and measures voltages v of all the measurement points that are registered in the measurement point table  13   c . As an example of a method of measuring the voltages, there is a simulation such as a PEEC method. However, the method of measuring the voltages is not limited thereto, but an arbitrary method can be used. 
     Then, the measurement unit  14   b  selects one measurement point, which has not been selected, out of all the measurement points registered in the measurement point table  13   c . Thereafter, the measurement unit  14   b  registers information, which is registered in the measurement point table  13   c , corresponding to the selected measurement point in association with a voltage v at the selected measurement point in the measurement point table  13   c , thereby updating the measurement point table  13   c . The measurement unit  14   b  repeatedly performs the process of updating the measurement point table  13   c  by registering the information in the measurement point table  13   c  in association with the voltage v at the selected measurement point until there is no measurement point that has not been selected. In this way, for example, as illustrated in the previous example represented in  FIG. 5 , voltage values at the measurement points are recorded in the measurement point table  13   c.    
     The drawing unit  14   c  draws the voltages of the planes that are measured by the measurement unit  14   b  on a graph having the voltage as one axis and having the layer as the other axis. A specific example will be described. First, the drawing unit  14   c  acquires the measurement point table  13   c  and specifies a minimal voltage v 1  from the measurement point table  13   c . In addition, the drawing unit  14   c  specifies a maximal voltage v 2  from the measurement point table  13   c . Furthermore, the drawing unit  14   c  specifies a minimal layer number z 1  from the measurement point table  13   c . In addition, the drawing unit  14   c  specifies a maximal layer number z 2  from the measurement point table  13   c . For example, in a case where the measurement point table  13   c  illustrated in the example represented in  FIG. 5  is acquired, the drawing unit  14   c  specifies a minimal voltage 1.420 [V], a maximal voltage 1.500 [V], a minimal layer number L 1 , and a maximal layer number L 3 . 
     Then, the drawing unit  14   c  generates a drawing area, which can include a rectangular area {(v 1 , z 1 ), (v 2 , z 1 ), (v 2 , z 2 ), (v 1 , z 1 )} and constituent elements such as axes, for a graph. Then, the drawing unit  14   c  draws the X axis that includes section [v 1 , v 2 ] in the drawing area. In addition, the drawing unit  14   c  draws the Y axis that includes section [z 1 , z 2 ] in the drawing area. 
       FIG. 12  is a diagram that illustrates an example of the X axis and the Y axis that are drawn by the drawing unit. In the example represented in  FIG. 12 , a drawing area  20  that is generated by the drawing unit  14   c  is illustrated. Such a drawing area  20  is an area that can include a rectangular area {(v 1 , z 1 ), (v 2 , z 1 ), (v 2 , z 2 ), (v 1 , z 1 )} and constituent elements such as axes. In the example represented in  FIG. 12 , a case is illustrated as an example in which the X axis including section [1.420, 1.500] is drawn in the drawing area  20  by the drawing unit  14   c . In addition, in the example represented in  FIG. 12 , a case is illustrated as an example in which the Y axis including section [L 1 , L 3 ] is drawn in the drawing area  20  by the drawing unit  14   c . Furthermore, in the example represented in  FIG. 12 , a case is illustrated as an example in which the drawing unit  14   c  draws a “voltage [V]” in correspondence with the X axis and draws a “layer number” in correspondence with the Y axis. 
     Subsequently, the drawing unit  14   c  determines whether or not there is a plane p that has not been selected out of planes of which identification numbers are registered in the measurement point table  13   c . In a case where there is a plane p that has not been selected, the drawing unit  14   c  selects one plane p that has not been selected. Then, the drawing unit  14   c  specifies a minimal voltage v 3  and a maximal voltage v 4  of the selected plane p and a layer z of the selected plane p from the measurement point table  13   c . Thereafter, the drawing unit  14   c  draws a segment (v 3 , z)-(v 4 , z) in the drawing area of the graph. The drawing unit  14   c  repeatedly performs such a process until there is no plane p that has not been selected.  FIG. 13  is a diagram that illustrates an example of a segment formed by a minimal voltage and a maximal voltage of each plane that is drawn by the drawing unit. In the example represented in  FIG. 13 , a case is illustrated as an example in which a segment (1.475, L 1 )-(1.500, L 1 ) is drawn in the drawing area of the graph by the drawing unit  14   c . In addition, in the example represented in  FIG. 13 , a case is illustrated as an example in which a segment (1.440, L 3 )-(1.460, L 3 ) is drawn in the drawing area of the graph by the drawing unit  14   c . Furthermore, in the example represented in  FIG. 13 , a case is illustrated as an example in which a segment (1.450, L 3 )-(1.465, L 3 ) is drawn in the drawing area of the graph by the drawing unit  14   c . In addition, in the example represented in  FIG. 13 , a case is illustrated as an example in which a segment (1.435, L 2 )-(1.470, L 2 ) is drawn in the drawing area of the graph by the drawing unit  14   c . Furthermore, in the example represented in  FIG. 13 , a case is illustrated as an example in which a segment (1.420, L 1 )-(1.430, L 1 ) is drawn in the drawing area of the graph by the drawing unit  14   c.    
     In this way, the drawing device  10  according to this embodiment draws voltages of planes on the graph in which the voltage is set on the X axis, and the layer is set on the Y axis. Therefore, according to the drawing device  10 , an image can be presented from which the appearance of a voltage drop of each plane in the laminated circuit board can be perceived in an easy manner. 
     Subsequently, the drawing unit  14   c  determines whether or not there is a record that has not been selected out of records in which the “via” is registered in the entry in which the type of an element is registered in the connection table  13   d . In a case where there is a record that has not been selected, the drawing unit  14   c  selects one record that has not been selected. Then, the drawing unit  14   c  specifies a set (m′, m) of identifiers of measurement points that are included in the selected record. Thereafter, the drawing unit  14   c  specifies a voltage v(m′) at the measurement point that is represented by the identifier stored in parameter m′ from the measurement point table  13   c . In addition, the drawing unit  14   c  specifies a voltage v(m) at the measurement point that is represented by the identifier m from the measurement point table  13   c . Furthermore, the drawing unit  14   c  specifies a layer number z(m′) of a layer in which a measurement point represented by the identifier stored in parameter m′ is present from the measurement point table  13   c . In addition, the drawing unit  14   c  specifies a layer number z(m) of a layer in which the measurement point represented by the identifier m is present from the measurement point table  13   c . Thereafter, the drawing unit  14   c  draws a segment (v(m′), z(m′))-(v(m), z(m)) in the drawing area of the graph. Here, the segment (v(m′), z(m′))-(v(m), z(m)) is a segment that represents a voltage drop of a via that has measurement points corresponding to the identifiers m′ and m. The drawing unit  14   c  repeatedly performs such a process until there is no record that has not been selected out of records in which the “via” is registered in the entry in which the type of an element is registered in the connection table  13   d . Then, in a case where there is no record that has not been selected, the drawing unit  14   c  stores image data  13   e  of the graph for which various kinds of drawing processes have been performed in the storage unit  13 . 
       FIG. 14  is a diagram that illustrates an example of a segment representing a voltage drop of a via that is drawn by the drawing unit. A graph that is illustrated in the example represented in  FIG. 14  represents a case where the drawing unit  14   c  draws a segment representing a voltage difference between two measurement point included in each via in addition to the drawn content of the graph illustrated in the example represented in  FIG. 13 . 
     In this way, the drawing device  10  according to this embodiment draws a voltage of each via on the graph in which the voltage is set on the X axis, and the layer is set on the Y axis. Therefore, according to the drawing device  10 , an image can be presented from which the appearance of a voltage drop of each via in the laminated circuit board can be perceived in an easy manner. 
     The display control unit  14   d  acquires the image data  13   e  that is generated by the drawing unit  14   c  and is stored in the storage unit  13  and performs controls of a display that is made by the display unit  12  such that an image represented by the image data  13   e  is displayed. Here, for example, this image is a graph as illustrated in the previous example represented in  FIG. 14 . 
       FIG. 15  is a diagram that illustrates the correspondence relation between the generated graph and a plane, a via, a power supplying pin, and a power consuming pin of the laminated circuit board. As illustrated in the example represented in  FIG. 15 , the drawing device  10  according to this embodiment can generate a graph from which the appearance of voltage drops of the via, and the like can be perceived in an easy manner. In this way, according to the drawing device  10  of this embodiment, an image from which an analysis of the laminated circuit board can be easily performed can be generated. 
     As described above, the drawing device  10  according to this embodiment draws the appearance of a voltage drop of each plane on a graph in which the voltage is set on the X axis and the layer is set on the Y axis. Then, the drawing device  10  performs control such that the drawn graph is displayed. Therefore, according to the drawing device  10 , control can be performed such that an image from which the appearance of a voltage drop of each plane in the laminated circuit board can be easily perceived is displayed. 
     In addition, the drawing device  10  according to this embodiment draws the appearance of a voltage drop of each via on a graph in which the voltage is set on the X axis and the layer is set on the Y axis. Therefore, according to the drawing device  10 , control can be performed such that an image from which the appearance of a voltage drop of each via in the laminated circuit board can be easily perceived is displayed. 
     The control unit  14  is an integrated circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA) or an electronic circuit such as a central processing unit (CPU) or a micro processing unit (MPU). 
     Flow of Process 
     Next, the flow of the process of the drawing device  10  according to this embodiment will be described.  FIG. 16  is a flowchart that illustrates the sequence of a drawing process according to the first embodiment. The drawing process, for example, is performed at timing when an instruction for performing the drawing process is received from the input unit  11  by the control unit  14 . 
     As illustrated in  FIG. 16 , the recording unit  14   a  performs a recording process in Step S 101 . Then, the measurement unit  14   b  performs a measurement process in Step S 102 . Subsequently, the drawing unit  14   c  performs a coordinate axis drawing process in Step S 103 . Thereafter, the drawing unit  14   c  performs a plane voltage drop drawing process in Step S 104 . Then, the drawing unit  14   c  performs a via voltage drop drawing process in Step S 105 . Thereafter, the display control unit  14   d  performs control of a display made by the display unit  12  so as to display a graph represented by image data  13   e  in Step S 106 , and the process ends. 
       FIGS. 17 and 18  are flowcharts that illustrate the sequence of a recording process according to the first embodiment. As illustrated in  FIG. 17 , the recording unit  14   a  acquires the first CAD data  13   a  and the second CAD data  13   b  from the storage unit  13  in Step S 201 . Then, the recording unit  14   a  determines whether or not there is an element that has not been selected out of a plurality of elements that are represented by the first CAD data  13   a  in Step S 202 . In a case where there is no element that has not been selected (No in Step S 202 ), the recording unit  14   a  stores the processing result in an internal memory, and the process is returned. On the other hand, in a case where there is an element that has not been selected (Yes in Step S 202 ), the recording unit  14   a  selects one element that has not been selected out of the plurality of elements that are represented by the first CAD data  13   a  in Step S 203 . Thereafter, the recording unit  14   a  stores the type of the selected element in parameter t, thereby updating the registered content of parameter t in Step S 204 . Then, the recording unit  14   a  stores coordinates at which the selected element is located in parameter (x, y), thereby updating the registered content of parameter (x, y) in Step S 205 . Thereafter, the recording unit  14   a  sorts layers of planes to which the selected element can be connected in the ascending order in Step S 206 . 
     Then, the recording unit  14   a  determines whether or not there is a layer z that has not been selected out of the layers sorted in the ascending order in Step S 207 . In a case where there is no layer z that has not been selected (No in Step S 207 ), the process is returned to Step S 202 . On the other hand, in a case where there is a layer z that has not been selected (Yes in Step S 207 ), the recording unit  14   a  selects one layer that is a layer z having not been selected out of the sorted layers and is a layer z having a least layer number in Step S 208 . Then, the recording unit  14   a  determines whether or not there is a plane p that has not been selected out of planes that are present in the selected layer z by referring to the second CAD data  13   b  in Step S 209 . In a case where there is no plane p that has not been selected (No in Step S 209 ), the process is returned to Step S 207 . 
     On the other hand, in a case where there is a plane p that has not been selected (Yes in Step S 209 ), the recording unit  14   a  selects one plane p that has not been selected out of planes that are present in the selected layer z in Step S 210 . Then, the recording unit  14   a  determines whether or not the coordinates stored in parameter (x, y) are present inside the area of the selected plane p by referring to the second CAD data in Step S 211 . In a case where the coordinates are not present therein (No in Step S 211 ), the process is returned to Step S 209 . 
     On the other hand, in a case where the coordinates are present therein (Yes in Step S 211 ), the recording unit  14   a  performs a process as follows. That is, the recording unit  14   a  records the value of the x coordinate and the value of the y coordinate of the coordinates stored in parameter (x, y), the layer number of the selected layer z, the identifier of the selected plane p, and the type of the element that is stored in parameter t in the measurement point table  13   c  in association with the identifier m of the measurement point in Step S 212 . 
     Then, the recording unit  14   a  determines whether or not the type of the element that is stored in parameter t is the via in Step S 213 . In a case where the type is not the via (No in Step S 213 ), the recording unit  14   a  records the value of the x coordinate and the value of the y coordinate of the coordinates stored in parameter (x, y) and the type of an element that is stored in parameter t in association with the identifier m of the measurement point in the connection table  13   d  in Step S 214 , and the process is returned to Step S 209 . 
     On the other hand, in a case where the type is the via (Yes in Step S 213 ), the recording unit  14   a  determines whether or not the selected layer z is an uppermost layer of the sorted layers in Step S 215 . In the case of the uppermost layer (Yes in Step S 215 ), the recording unit  14   a  stores the identifier m of the measurement point in parameter m′, updates the registered content of parameter m′ in Step S 217 , and the process is returned to Step S 209 . 
     On the other hand, in a case where the selected layer is not an uppermost layer (No in Step S 215 ), the recording unit  14   a  performs a process as follows. That is, the recording unit  14   a  records the value of the x coordinate and the value of the y coordinate of the coordinates stored in parameter (x, y) and the type of the element that is stored in parameter t in the connection table  13   d  in association with the identifier m of the measurement point and the identifier of the measurement point that is stored in parameter m′ in Step S 216 . Then, the process proceeds to Step S 217 . 
       FIG. 19  is a flowchart that illustrates the sequence of a measurement process according to the first embodiment. As illustrated in  FIG. 19 , the measurement unit  14   b  acquires the measurement point table  13   c  from the storage unit  13  and measures voltages v of all the measurement points registered in the measurement point table  13   c  in Step S 301 . 
     Then, the measurement unit  14   b  determines whether or not there is a measurement point that has not been selected out of all the measurement points registered in the measurement point table  13   c  in Step S 302 . In a case where there is no measurement point that has not been selected (No in Step S 302 ), the measurement unit  14   b  stores the processing result in an internal memory, and the process is returned. On the other hand, in a case where there is a measurement point that has not been selected (Yes in Step S 302 ), the measurement unit  14   b  selects one measurement point that has not been selected out of all the measurement points registered in the measurement point table  13   c  in Step S 303 . Thereafter, the measurement unit  14   b  registers information that is registered in the measurement point table  13   c  that corresponds to the selected measurement point in the measurement point table  13   c  in association with the voltage v at the selected measurement point so as to update the measurement point table  13   c  in Step S 304 , and the process proceeds to Step S 302 . 
       FIG. 20  is a flowchart that illustrates the sequence of a coordinate-axis drawing process according to the first embodiment. As illustrated in  FIG. 20 , the drawing unit  14   c  acquires the measurement point table  13   c  and specifies a minimal voltage v 1  from the measurement point table  13   c  in Step S 401 . Then, the drawing unit  14   c  specifies a maximal voltage v 2  from the measurement point table  13   c  in Step S 402 . Subsequently, the drawing unit  14   c  specifies a minimal layer number z 1  from the measurement point table  13   c  in Step S 403 . Thereafter, the drawing unit  14   c  specifies a maximal layer number z 2  from the measurement point table  13   c  in Step S 404 . 
     Then, the drawing unit  14   c  generates a drawing area, which can include a rectangular area {(v 1 , z 1 ), (v 2 , z 1 ), (v 2 , z 2 ), (v 1 , z 1 )} and constituent elements such as axes, for a graph in Step S 405 . Subsequently, the drawing unit  14   c  draws the X axis that includes section [v 1 , v 2 ] in the drawing area in Step S 406 . Thereafter, the drawing unit  14   c  draws the Y axis that includes section [z 1 , z 2 ] in the drawing area in Step S 407  and stores the processing result in the internal memory, and the process is returned. 
       FIG. 21  is a flowchart that illustrates the sequence of a plane voltage drop drawing process according to the first embodiment. As illustrated in  FIG. 21 , the drawing unit  14   c  determines whether or not there is a plane p that has not been selected out of planes of which the identification numbers are registered in the measurement point table  13   c  in Step S 501 . In a case where there is no plane p that has not been selected (No in Step S 501 ), the drawing unit  14   c  stores the processing result in the internal memory, and the process is returned. On the other hand, in a case where there is a plane p that has not been selected (Yes in Step S 501 ), the drawing unit  14   c  selects one plane p that has not been selected in Step S 502 . Then, the drawing unit  14   c  specifies a minimal voltage v 3  and a maximal voltage v 4  of the selected plane p and the layer z of the selected plane p from the measurement point table  13   c  in Step S 503 . Thereafter, the drawing unit  14   c  draws a segment (v 3 , z)-(v 4 , z) in the drawing area of the graph in Step S 504 , and the process is returned to Step S 501 . 
       FIG. 22  is a flowchart that illustrates the sequence of a via voltage drop drawing process according to the first embodiment. As illustrated in  FIG. 22 , the drawing unit  14   c  determines whether or not there is a record that has not been selected out of records in which the via is registered in the entry in which the type of an element is registered in the connection table  13   d  in Step S 601 . In a case where there is a record that has not been selected (Yes in Step S 601 ), the drawing unit  14   c  selects one record that has not been selected in Step S 602 . Then, the drawing unit  14   c  specifies a set (m′, m) of identifiers of measurement points that are included in the selected record in Step S 603 . Thereafter, the drawing unit  14   c  specifies a voltage v(m′) at the measurement point that is represented by the identifier stored in parameter m′ from the measurement point table  13   c  in Step S 604 . Subsequently, the drawing unit  14   c  specifies a voltage v(m) at the measurement point represented by the identifier m from the measurement point table  13   c  in Step S 605 . Then, the drawing unit  14   c  specifies a layer number z(m′) of a layer in which the measurement point represented by the identifier that is stored in parameter m′ is present from the measurement point table  13   c  in Step S 606 . Subsequently, the drawing unit  14   c  specifies a layer number z(m) of the layer in which the measurement point represented by the identifier m is present from the measurement point table  13   c  in Step S 607 . Thereafter, the drawing unit  14   c  draws a segment (v(m′), z(m′))-(v(m), z(m)) in the drawing area of the graph in Step S 608 , and the process is returned to Step S 601 . 
     On the other hand, in a case where there is no record that has not been selected (No in Step S 601 ), the drawing unit  14   c  stores the image data  13   e  of the graph in the storage unit  13  in Step S 609  and stores the processing result in the internal memory, and the process is returned. 
     As described above, the drawing device  10  according to this embodiment draws the appearance of a voltage drop of each plane on a graph in which the voltage is set on the X axis, and the layer is set on the Y axis. Then, the drawing device  10  performs control so as to display the drawn graph. Therefore, according to the drawing device  10 , it can be controlled to display an image from which the appearance of a voltage drop of each plane in the laminated circuit board can be easily perceived. 
     In addition, the drawing device  10  according to this embodiment draws the appearance of a voltage drop of each via on a graph in which the voltage is set on the X axis, and the layer is set on the Y axis. Therefore, according to the drawing device  10 , it can be controlled to display an image from which the appearance of a voltage drop of each via in the laminated circuit board can be easily perceived. 
     [b] Second Embodiment 
     In a second embodiment, a case will be described in which information representing the magnitude of a current flowing through a via is drawn on a graph. 
     Configuration of Drawing Device  30   
       FIG. 23  is a diagram that illustrates an example of the functional configuration of a drawing device according to the second embodiment. As illustrated in  FIG. 23 , a drawing device  30  includes a storage unit  33  and a control unit  34 . A difference between the stored contents of the storage unit  33  and the storage unit  13  according to the first embodiment illustrated in  FIG. 1  is that a connection table  33   d  is stored instead of the connection table  13   d  in the storage unit  33 . In addition, a difference between the control unit  34  and the control unit  14  according to the first embodiment illustrated in  FIG. 1  is that a measurement unit  34   b  and a drawing unit  34   c  are included in the control unit  34 . Hereinafter, the same reference numeral as that illustrated in  FIG. 1  is assigned to each unit or each device that achieves the same function as that of the first embodiment, and the description thereof will not be presented. 
       FIG. 24  is a diagram that illustrates an example of the data structure of the connection table according to the second embodiment. In the connection table  33   d  illustrated in the example represented in  FIG. 24 , the value of a current i [A] flowing between two measurement points of the same via is registered by the measurement unit  34   b  to be described below, in addition to the registered content of the connection table  13   d  according to the first embodiment. The example represented in  FIG. 24  illustrates that a current of 0.300 [A] flows between two measurement points of a via that has the two measurement points represented by two identifiers m 002  and m 003 . The other vias are similarly applied. 
     The storage unit  33 , for example, is a semiconductor memory device such as a flash memory or a storage device such as a hard disk or an optical disc. The storage unit  33  is not limited to the storage device of a type described above and may be a random access memory (RAM) or a read only memory (ROM). 
     The measurement unit  34   b  has a function of performing a process as follows in addition to the functions of the measurement unit  14   b  according to the first embodiment. That is, for each set (m′, m) of all the identifiers in which identifiers are registered as the set (m′, m) in the connection table  33   d , the measurement unit  34   b  measures a current i between measurement points that correspond to the set (m′, m). Subsequently, the measurement unit  34   b  determines whether or not there is a set (m′, m) that has not been selected out of sets (m′, m) of identifiers that are registered in the connection table  33   d . In a case where there is a set (m′, m) that has not been selected, the measurement unit  34   b  selects one set (m′, m) that has not been selected out of sets (m′, m) of the identifiers that are registered in the connection table  33   d . Then, the measurement unit  34   b  registers the current i between two measurement points represented by the set (m′, m) of selected identifiers in the connection table  33   d  in association with the set (m′, m) of the selected identifiers. As a result, as illustrated in the example represented in  FIG. 24 , the magnitude of a current flowing through two measurement points included in the via is registered in the connection table  33   d . The measurement unit  34   b  repeatedly performs such a process until there is no set (m′, m) that has not been selected. 
     The drawing unit  34   c  determines whether or not there is a record that has not been selected out of records in which the via is recorded in the entry in which the type of an element is recorded in the connection table  33   d . In a case where there is a record that has not been selected, the drawing unit  34   c  selects one record that has not been selected. Then, the drawing unit  34   c  specifies a set (m′, m) of identifiers of measurement points that are included in the selected record. Thereafter, the drawing unit  34   c  specifies a voltage v(m′) at the measurement point that is represented by the identifier stored in parameter m′ from the measurement point table  13   c . In addition, the drawing unit  34   c  specifies a voltage v(m) at the measurement point that is represented by the identifier m from the measurement point table  13   c . Furthermore, the drawing unit  34   c  specifies a layer number z(m′) of a layer in which a measurement point represented by the identifier stored in parameter m′ is present from the measurement point table  13   c . In addition, the drawing unit  34   c  specifies a layer number z(m) of a layer in which the measurement point represented by the identifier m is present from the measurement point table  13   c . Thereafter, the drawing unit  34   c  specifies a current i between two measurement points corresponding to the set (m′, m) of the identifiers of the measurement points from the connection table  33   d . Then, the drawing unit  34   c  determines a thickness for drawing based on the magnitude of the specified current i. For example, the drawing unit  34   c  determines such that, the larger the magnitude of the current i is, the larger the thickness for drawing is. 
     Subsequently, the drawing unit  34   c  determines a direction in which the current i flows based on the magnitude relation of voltages v(m′) and v(m). Then, the drawing unit  34   c  performs drawing for the drawing area of the graph such that a segment (v(m′), z(m′))-(v(m), z(m)) is an arrow representing the direction in which the current i flows and has a thickness that is determined for drawing a line. The drawing unit  34   c  repeatedly performs such a process until there is no record that has not been selected out of records in which the via is registered in the entry in which the type of an element is registered in the connection table  33   d . Then, in a case where there is no record that has not been selected, the drawing unit  34   c  stores the image data  13   e  of the graph for which the drawing process is performed in the storage unit  33 . 
       FIG. 25  is a diagram that illustrates an example of a segment that represents the magnitude of a current flowing through a via that is drawn by the drawing unit. As illustrated on the graph of the example represented in  FIG. 25 , the thickness of a segment that corresponds to a via portion corresponds to the magnitude of the current. Accordingly, the magnitude of the current flowing through each via in the laminated circuit board can be perceived from the graph in an easy manner. 
     In this way, the drawing device  30  according to this embodiment draws a segment that represents the magnitude of the current flowing through each via on the graph in which the voltage is set on the X axis, and the layer is set on the Y axis. Therefore, according to the drawing device  30 , an image can be presented from which the appearance of the magnitude of the current flowing through each via in the laminated circuit board can be perceived in an easy manner. In addition, the drawing unit  34   c  may determine a color of a segment that corresponds to the magnitude of the current i based on the magnitude of the current i and perform drawing such that the color of the segment (v(m′), z(m′))-(v(m), z(m)) is a determined color. 
     The control unit  34  is an integrated circuit such as an ASIC or an FPGA or an electronic circuit such as a CPU or an MPU. 
     Flow of Process 
     Next, the flow of the process performed by the drawing device  30  according to this embodiment will be described. The process contents of a measurement process and a via voltage drop drawing process according to this embodiment are different from those of the measurement process and the via voltage drop drawing process according to the first embodiment illustrated in  FIG. 16 . 
       FIG. 26  is a flowchart that illustrates the sequence of the measurement process according to the second embodiment. As illustrated in  FIG. 26 , the processes of steps S 301  to S 304  are the same as those of the first embodiment. In Step S 302 , in a case where it is determined that there is no measurement point that has not been selected (No in Step S 302 ), for each set (m′, m) of all the identifiers in which the identifiers are registered as the set (m′, m) in the connection table  33   d , the measurement unit  34   b  measures a current i between measurement points that correspond to the set (m′, m) in Step S 701 . 
     Subsequently, the measurement unit  34   b  determines whether or not there is a set (m′, m) that has not been selected out of the sets (m′, m) of identifiers registered in the connection table  33   d  in Step S 702 . In a case where there is no set (m′, m) that has not been selected (No in Step S 702 ), the measurement unit  34   b  stores the process result in an internal memory, and the process is returned. On the other hand, in a case where there is a set (m′, m) that has not been selected (Yes in Step S 702 ), the measurement unit  34   b  selects one set (m′, m) that has not been selected out of the sets (m′, m) of identifiers that are registered in the connection table  33   d  in Step S 703 . Then, the measurement unit  34   b  registers the current between two measurement points represented by the selected set (m′, m) of the identifiers in the connection table  33   d  in association with the selected set (m′, m) of the identifiers in Step S 704 , and the process is returned to Step S 702 . 
       FIG. 27  is a flowchart that illustrates the sequence of a via voltage drop drawing process according to the second embodiment. As illustrated in  FIG. 27 , the processes of Steps S 601  to S 607  and S 609  are the same as those of the first embodiment. As illustrated in  FIG. 27 , after the process of Step S 607 , the drawing unit  34   c  specifies a current i between two measurement points that correspond to a set (m′, m) of identifiers of the measurement points from the connection table  33   d  in Step S 801 . Then, the drawing unit  34   c  determines a thickness for drawing based on the magnitude of the specified current i in Step S 802 . 
     Subsequently, the drawing unit  34   c  determines a direction in which the current i flows based on the magnitude relation of voltages v(m′) and v(m) in Step S 803 . Then, the drawing unit  34   c  performs drawing for the drawing area of the graph such that a segment (v(m′), z(m′))-(v(m), z(m)) is an arrow that represents the direction in which the current i flows and has a determined thickness for drawing a line in Step S 804 , and the process is returned to Step S 601 . 
     As described above, the drawing device  30  according to this embodiment draws the appearance of a voltage drop of each plane on a graph having the voltage set on the X axis and having the layer set on the Y axis. Then, the drawing device  30  performs control so as to display the drawn graph. Therefore, according to the drawing device  30 , it can be controlled to display an image from which the appearance of a voltage drop of each plane in the laminated circuit board can be perceived in an easy manner. 
     In addition, the drawing device  30  according to this embodiment draws the appearance of a voltage drop of each via on a graph having the voltage set on the X axis and having the layer set on the Y axis. Therefore, according to the drawing device  30 , it can be controlled to display an image from which the appearance of a voltage drop of each via in the laminated circuit board can be perceived in an easy manner. 
     Furthermore, the drawing device  30  according to this embodiment draws a segment that represents the magnitude of a current flowing through each via in a thickness or a color on a graph having the voltage set on the X axis and having the layer set on the Y axis. Therefore, according to the drawing device  30 , it can be controlled to display an image from which the appearance of the magnitude of a current of each via in the laminated circuit board can be perceived in an easy manner. 
     [c] Third Embodiment 
     In a third embodiment, a case will be described in which information representing the magnitude of a current flowing through a plane is drawn on a graph.  FIG. 28  is a schematic diagram of a laminated circuit board in a case where there is a plurality of paths joining two points in a net and the paths go through planes that are different from each other. The laminated circuit board illustrated in the example represented in  FIG. 28  includes a plane of layer number L 1  and a plane of layer number L 3  in which almost the same voltage drop occurs. In such a case, in the third embodiment, by presenting the magnitudes of a current flowing through the plane of layer number L 1  and a current flowing through the plane of layer number L 3  in which the voltage drops are the same, it can be perceived that the resistance of the plane of one layer is higher than that of the other layer. 
     Configuration of Drawing Device  40   
       FIG. 29  is a diagram that illustrates an example of the functional configuration of a drawing device according to the third embodiment. As illustrated in  FIG. 29 , a drawing device  40  includes a storage unit  43  and a control unit  44 . A difference between the storage unit  43  and the storage unit  33  according to the second embodiment illustrated in  FIG. 23  is that a connection table  43   d  is stored in the storage unit  43 . In addition, a difference between the control unit  44  and the control unit  34  according to the second embodiment illustrated in  FIG. 23  is that a measurement unit  44   b  and a drawing unit  44   c  are included in the control unit  44 . Hereinafter, the same reference numeral as that illustrated in  FIG. 1  or  FIG. 23  is assigned to each unit or each device that achieves the same function as that of the first embodiment or the second embodiment described above, and the description thereof will not be presented. 
       FIG. 30  is a diagram that illustrates an example of the data structure of a connection table according to the third embodiment. In the connection table  43   d  of the example represented in  FIG. 30 , a value of a current i [A] flowing through the measurement point of the power supplying pin and a measurement point of the power consuming pin is registered by the measurement unit  44   b  in addition to the registered content of the connection table  33   d  according to the second embodiment. In the example represented in  FIG. 30 , a case is illustrated in which a current of −0.300 [A] flows through the measurement point of the power supplying pin and a current of 0.300 [A]flows through the measurement point of the power consuming pin. In addition, the value of a current i [A] that flows through the measurement point of the power supplying pin and the measurement point of the power consuming pin is assumed to be input by a user using the drawing device  40  through an input unit  11 . 
     The storage unit  43 , for example, is a semiconductor memory device such as a flash memory or a storage device such as a hard disk or an optical disc. The storage unit  33  is not limited to the storage device of a type described above and may be a random access memory (RAM) or a read only memory (ROM). 
     The measurement unit  44   b  has a function of performing a process as follows in addition to the functions of the measurement unit  34   b  according to the second embodiment. The measurement unit  44   b  registers a value of a current i [A] that flows through the measurement point of the power supplying pin and the measurement point of the power consuming pin that is input through the input unit  11  in the connection table  43   d . In addition, the measurement unit  44   b  generates a table (sorted table) that is acquired by sorting the measurement point table  13   c  with respect to the voltage v in the ascending order.  FIGS. 31 and 32  are diagrams that illustrate an example of a method of generating the sorted table.  FIG. 31  is a diagram that illustrates an example of the measurement point table  13   c .  FIG. 32  is a sorted table that is acquired as a result of sorting the measurement point table  13   c  illustrated in the example represented in  FIG. 31  with respect to the voltage v in the ascending order. For example, the measurement unit  44   b  sorts the measurement point table  13   c  with respect to the voltage v in the ascending order using the measurement point table  13   c  illustrated in the example represented in  FIG. 31 , thereby generating the sorted table that is illustrated in the example represented in  FIG. 32 . Subsequently, the measurement unit  44   b  sets the value of parameter is(p) in which a current value is stored to zero for all the planes p. 
     Then, the measurement unit  44   b  determines whether or not there is a measurement point that has not been selected by referring to the sorted table. In a case where there is a measurement point that has not been selected, the measurement unit  44   b  selects a measurement point, which has not been selected, that is a measurement point m 1  having a lowest voltage v out of measurement points of which voltages v are sorted in the ascending order. In addition, the measurement unit  44   b  can select a plurality of measurement points in a case where there is a plurality of measurement points having the same values of voltages v. Thereafter, the measurement unit  44   b  specifies a measurement point m 2  having a voltage v that is higher than that at the measurement point m 1  and is closest to the voltage at the measurement point m 1  out of the other measurement points in the plane p having the measurement point m 1 . For example, a case will be described in which the sorted table illustrated in the example represented in  FIG. 32  is used. The measurement unit  44   b  performs a process as follows in a case where a measurement point represented by an identifier m 010  illustrated in the example represented in  FIG. 32  is selected. The measurement unit  44   b  specifies a measurement point of an identifier m 012  having a voltage that is higher than a voltage 1.201 [V] and is closest to the voltage 1.201 [V] out of the other measurement points (measurement points of identifiers m 012  and m 014 ) in a plane (plane p 003 ) that includes the measurement point of the identifier m 010 . 
     Subsequently, the measurement unit  44   b  determines whether or not the measurement point m 2  is specified. In a case where the measurement point m 2  is not specified, the above-described process of determining whether or not there is a measurement point that has not been selected is performed again, and, as described above, the subsequent processes after the process of determining whether or not there is a measurement point that has not been selected are performed again. 
     On the other hand, in a case where the measurement point m 2  is specified, the measurement unit  44   b  adds a sum of a current flowing into the measurement point m 1  of the plane p and a current flowing out of the measurement point m 1  to the value of is(p), thereby updating the value of is(p). 
     A specific example will be described.  FIG. 33  is a diagram that illustrates an example of the connection table.  FIG. 34  is a schematic diagram that illustrates some vias and some planes that are represented by the sorted table illustrated in the example represented in  FIG. 32 . A case will be described in which the measurement unit  44   b  selects a measurement point represented by an identifier m 010  by referring to the sorted table illustrated in the example represented in  FIG. 32 . In such a case, the measurement unit  44   b , as illustrated in the example represented in  FIG. 34 , specifies a measurement point (a measurement point of which the identifier is m 012 ) that has a lowest voltage next to a measurement point (a measurement point of which the identifier is m 010 ) of the lowest voltage 1.201 [V] for the plane represented by the identifier p 003 . The voltage at the measurement point of which the identifier is m 012  is 1.205 [V], and an equipotential surface of a voltage 1.205 [V] is present in the plane represented by the identifier p 003 . Here, by referring to the connection table  43   d  illustrated in the example represented in  FIG. 33 , a record in which the measurement point of the identifier m 010  is registered is located in the first row. Here, a current of 1.0 [A] flows from the measurement point of which the identifier is m 010  to the measurement point of which the identifier is m 051 . In other words, a current of 1.0 [A] flows in a direction flowing out from the plane represented by the identifier p 003 . In such a case, the measurement unit  44   b  adds a positive value “1.0” to the value of is(p 003 )=0, thereby updating the value of is(p 003 )=1.0. Here, is(p 003 ) after the update represents a magnitude of a current flowing into the measurement point m 010  from the plane represented by the identifier p 003 . In the plane represented by the identifier p 003 , the voltage exceeds the voltage of the measurement point m 010 , and flowing in/out of a current at a point having a voltage lower than the voltage of the equipotential surface that is the voltage of 1.205 [V] does not occur, and accordingly, is(p 003 ) after the update represents a passing current from the equipotential surface of the measurement point m 012  to the measurement point m 010 . 
     In addition, the measurement unit  44   b  performs a process as follows by referring to the measurement point table  13   c . The measurement unit  44   b  selects a measurement point (measurement point m 012 ) having a voltage that is lowest next to the voltage at the measurement point m 010  in the plane represented by the identifier p 003  and specifies a measurement point (measurement point m 014 ) having a voltage that is lowest next to the voltage at the measurement point m 012 . The voltage at the measurement point m 014  is 1.207 [V], and an equipotential surfaces having a voltage of 1.205 [V] is present on the plane that is represented by the identifier p 003 . Here, there are two records in which measurement point m 012  is registered when the connection table  43   d  illustrated in the example represented in  FIG. 33  is referred to. The first record represents that a current of 0.1 [A] flows from the measurement point m 012  to the measurement point m 052 . In other words, the first record represents that a current flows in a direction (the direction in which the current flows into the via) in which the current flows out from the plane represented by the identifier p 003 . The second record represents that a current of 0.3 [A] flows from measurement point m 053  to the measurement point m 012 . In other words, the second record represents that a current flows in a direction (a direction in which the current flows out from the via) in which the current flows into the plane represented by the identifier p 003 . 
     Here, a current flowing out from the plane is denoted as negative sign, and a current flowing into the plane is denoted by a positive sign. The measurement unit  44   b  adds to is(p 003 ) a value acquired by adding these currents, thereby updating the value. In other words, the measurement unit  44   b  updates the value to is(p 003 )=1.0−0.3+0.1=0.8 [A]. In the plane represented by the identifier p 003 , the voltage exceeds the voltage of the measurement point m 012 , and flowing in/out of a current at a point having a voltage lower than the voltage of the equipotential surface that is the voltage of 1.207 [V] does not occur, and accordingly, is(p 003 ) after the update represents a passing current that passes from the equipotential surface of the measurement point m 014  to the equipotential surface of the measurement point m 012 . 
     The measurement unit  44   b  performs the above-described process for all the planes with measurement points having voltages close to each other used as a pair within the same plane, whereby the magnitude of a current flowing through the plane can be measured. 
     The drawing unit  44   c  draws a segment (v(m 1 ), z)-(v(m 2 ), z) with a thickness that corresponds to the magnitude of the current value is(p) on a graph. For example, a case will be described in which a value of is(p 003 ) that corresponds to a segment (1.201, L 3 )-(1.205, L 3 ) is 1.0 [A], and a value of is(p 003 ) that corresponds to a segment (1.205, L 3 )-(1.207, L 3 ) is 0.8 [A]. In such a case, in a case where a thickness of the segment (1.201, L 3 )-(1.205, L 3 ) is set to “1”, the drawing unit  44   c  draws the segment (1.205, L 3 )-(1.207, L 3 ) with a thickness of “0.8”.  FIGS. 35 and 36  are diagrams that illustrate examples of the thickness of a segment that is drawn by the drawing unit. In the example represented in  FIG. 35 , a case is illustrated in which, in a case where a thickness of the segment (1.201, L 3 )-(1.205, L 3 ) is set to “1”, the drawing unit  44   c  draws the segment (1.205, L 3 )-(1.207, L 3 ) with a thickness of “0.8”. 
     The example represented in  FIG. 36  illustrates currents flowing through each plane of each layer in the laminated circuit board that is illustrated in the example represented in  FIG. 28 . In the example represented in  FIG. 36 , it can be easily perceived that the resistance of a plane, of which the layer number is L 1 , having a thinner segment is higher than the resistance of a plane of which the layer number is L 3 . 
     In addition, the drawing device  40  according to this embodiment draws a segment that represents the magnitude of the current flowing through each plane using a thickness or a color on a graph having the voltage set on the X axis and having the layer set on the Y axis. Therefore, according to the drawing device  40 , it can be controlled to display an image from which the appearance of the magnitude of a current flowing through each plane in the laminated circuit board can be perceived in an easy manner. 
     The control unit  44  is an integrated circuit such as an ASIC or an FPGA or an electronic circuit such as a CPU or an MPU. 
     Flow of Process 
     Next, the flow of the process performed by the drawing device  40  according to this embodiment will be described. The process content of a plane voltage drop drawing process according to this embodiment is different from that of the plane voltage drop drawing process according to the first embodiment illustrated in  FIG. 16 . 
       FIG. 37  is a flowchart that illustrates the sequence of the plane voltage drop drawing process according to the third embodiment. As illustrated in  FIG. 37 , the measurement unit  44   b  generates a table (sorted table) acquired by sorting the measurement point table  13   c  with respect to the voltage v in the ascending order in Step S 901 . Subsequently, the measurement unit  44   b  sets the value of parameter is(p) in which a current value is stored to zero for all the planes p in Step S 902 . 
     Then, the measurement unit  44   b  determines whether or not there is a measurement point that has not been selected by referring to the sorted table in Step S 903 . In a case where there is no measurement point that has not been selected (No in Step S 903 ), the measurement unit  44   b  stores the process result in an internal memory, and the process is returned. On the other hand, in a case where there is a measurement point that has not been selected (Yes in Step S 903 ), the measurement unit  44   b  selects a measurement point m 1  that has not been selected and has a lowest voltage v out of the measurement points that are sorted with respect to the voltage v in the ascending order in Step S 904 . Thereafter, the measurement unit  44   b  specifies a measurement point m 2  having a voltage v that is higher than the voltage at the measurement point m 1  and is closest to the voltage at the measurement point m 1  out of the other measurement points in the plane p that includes the measurement point m 1  in Step S 905 . 
     Subsequently, the measurement unit  44   b  determines whether or not the measurement point m 2  is specified in Step S 906 . In a case where the measurement point m 2  is not specified (No in Step S 906 ), the process is returned to Step S 903 . 
     On the other hand, in a case where the measurement point m 2  is specified (Yes in Step S 906 ), the measurement unit  44   b  adds a sum of the current flowing into the measurement point m 1  of the plane p and the current flowing out from the measurement point m 1  to the value of is(p), thereby updating the value of is(p) in Step S 907 . 
     Then, the drawing unit  44   c  draws a segment (v(m 1 ), z)-(v(m 2 ), z) with a thickness that corresponds to the magnitude of the current value is(p) on a graph in Step S 908 , and the process is returned to Step S 903 . 
     As described above, the drawing device  40  according to this embodiment draws the appearance of a voltage drop of each plane on the graph having the voltage set on the X axis and having the layer set on the Y axis. Then, the drawing device  40  performs control such that the drawn graph is displayed. Therefore, according to the drawing device  40 , control can be performed such that an image from which the appearance of a voltage drop of each plane in the laminated circuit board can be easily perceived is displayed. 
     In addition, the drawing device  40  according to this embodiment draws the appearance of a voltage drop of each via on a graph in which the voltage is set on the X axis and the layer is set on the Y axis. Therefore, according to the drawing device  40 , control can be performed such that an image from which the appearance of a voltage drop of each via in the laminated circuit board can be easily perceived is displayed. 
     Furthermore, the drawing device  40  according to this embodiment draws a segment that represents the magnitude of a current of each via in a thickness or a color on a graph having the voltage set on the X axis and having the layer set on the Y axis. Therefore, according to the drawing device  40 , control can be performed such that an image from which the appearance of the magnitude of a current of each via in the laminated circuit board can be easily perceived is displayed. 
     In addition, the drawing device  40  according to this embodiment draws a segment that represents the magnitude of a current flowing through each plane in a thickness or a color on a graph having the voltage set on the X axis and having the layer set on the Y axis. Therefore, according to the drawing device  40 , it can be controlled to display an image from which the appearance of the magnitude of a current of each plane in the laminated circuit board can be perceived in an easy manner. 
     Until now disclosed devices according to embodiments have been described. However, the present invention may be performed in various embodiments other than the above-described embodiments. Hereinafter, other embodiments belonging to the present invention will be described. 
     For example, whether a connection relation of measurement points in each embodiment is appropriate in the context of a display, in other words, a net connected to the power supplying pin is connected to the power consuming pin, and a determination process of determining whether the path of a voltage drop is present may be performed.  FIG. 38  is a diagram that illustrates an example of the functional configuration of a drawing device acquired by adding a function of the determination process to the drawing device according to each embodiment. The example represented in  FIG. 38  illustrates a case where a determination unit  54   d  is added to the drawing device  10  according to the first embodiment. In addition, the determination unit  54   d  may be disposed in the drawing device according to the second or third embodiment.  FIG. 39  is a flowchart that illustrates the sequence of a drawing process to which the determination process is added. As illustrated in FIG.  39 , after the recording process, the determination unit  54   d  performs the determination process in Step S 1001 . Then, the process proceeds to the measurement process. 
       FIGS. 40A and 40B  are flowcharts that illustrate the sequence of the determination process. As illustrated in  FIGS. 40A and 40B , the determination unit  54   d  determines whether or not there is a measurement point of which the type of the element in the measurement point table  13   c  is the power supplying pin in Step S 1101 . In a case where there is no measurement point of which the type of the element is the power supplying pin (No in Step S 1101 ), a determination unit  54  determines whether or not a determination table to be described later is blank in Step S 1113 . In a case where the determination table is not blank, the process ends with an error, and the drawing process is stopped. On the other hand, in a case where the determination table is blank, the determination unit  54  stores the process result in an internal memory, and the process is returned. 
     On the other hand, in a case where there is a measurement point of which the type of the element is the power supplying pin (Yes in Step S 1101 ), the determination unit  54  selects one measurement point, of which the type of the element is the power supplying pin, that has not been selected in the measurement point table  13   c  in Step S 1102 . Subsequently, the determination unit  54  registers all the measurement points of which the types of elements are the power consuming pins in the measurement point table  13   c  in Step S 1103 . 
     The determination unit  54  determines whether or not there is a measurement point mp that has not been selected out of measurement points mp that are present within the same plane as that of the selected measurement point in the measurement point table  13   c  in Step S 1104 . In a case where there is no measurement point mp that has not been selected (No in Step S 1104 ), the process is returned to Step S 1101 . On the other hand, in a case where there is a measurement point mp that has not been selected (Yes in Step S 1104 ), the determination unit  54  selects one measurement point mp that has not been selected and is within the same plane as that of the selected measurement point in Step S 1105 . Then, the determination unit  54  determines whether or not the type of the element including the selected measurement point mp is the power consuming pin in Step S 1106 . In a case where the type of the element is the power consuming pin (Yes in Step S 1106 ), the determination unit  54  removes the selected measurement point mp from the determination table in Step S 1107 , and the process is returned to Step S 1104 . 
     On the other hand, in a case where the type of the element is not the power consuming pin (No in Step S 1106 ), the determination unit  54  determines whether or not the type of the element including the selected measurement point mp is the via in Step S 1108 . In a case where the type of the element is not the via (No in Step S 1108 ), the process is returned to Step S 1104 . On the other hand, in a case where the type of the element is the via (Yes in Step S 1108 ), the determination unit  54  determines whether or not there is a measurement point my that has not been selected out of the other measurement points my included in the via that includes the selected measurement point mp in a connection table  43   e  in Step S 1109 . In a case where there is no measurement point my that has not been selected (No in Step S 1109 ), the process is returned to Step S 1104 . On the other hand, in a case where there is a measurement point my that has not been selected (Yes in Step S 1109 ), the determination unit  54  selects one measurement point my that has not been selected out of the other measurement points my included in the via that includes the selected measurement point mp in Step S 1110 . Then, the determination unit  54  determines whether or not the type of the element that includes the selected measurement point my is the power consuming pin in Step S 1111 . In a case where the type of the element is not the power consuming pin (No in Step S 1111 ), the process is returned to Step S 1109 . On the other hand, in a case where the type of the element is the power consuming pin (Yes in Step S 1111 ), the determination unit  54  removes the measurement point my from the determination table in Step S 1112 , and the process is returned to Step S 1109 . 
     Accordingly, in a case where the connection relation of measurement points is not appropriate in the context of a display such as a case where the path of a voltage drop is not present, the drawing process can be stopped. 
     For example, in each process described in each embodiment, the whole or a part of the process described as being automatically performed may be performed in a manual manner. In addition, the whole or a part of the process that has been described as being manually performed in each embodiment may be performed in an automatic manner by using a known method. 
     In addition, in accordance with various loads, the usage status, and the like, the process performed in each step of each process described in each embodiment may be arbitrarily divided in parts or may be put together. Furthermore, any step may be omitted. 
     Furthermore, in accordance with various loads, the usage status, and the like, the processing sequence in the steps of each process described in each embodiment may be changed. 
     In addition, each constituent element of each device illustrated in the diagram is a functional and conceptual element and does not necessarily need to be physically configured as illustrated in the diagram. In other words, a specific state of the division or integration of each device is not limited to that illustrated in the diagram, and the whole or a part thereof may be configured to be functionally or physically divided or integrated in an arbitrary unit in accordance with various loads, the usage status, and the like. 
     Drawing Program 
     Various kinds of processes performed by the drawing device  10 ,  30 , or  40  described in the above-described embodiment may be realized by executing a program that is prepared in advance using a computer system such as a personal computer or a workstation. Thus, hereinafter, an example of a computer that executes drawing program that has the same function as that of the drawing device  10 ,  30 , or  40  described in the above-described embodiment will be described with reference to  FIG. 41 .  FIG. 41  is a diagram that illustrates the computer that executes the drawing program. 
     As illustrated in  FIG. 41 , a computer  300  includes a CPU  310 , a ROM  320 , an HDD  330 , and a RAM  340 . The CPU  310 , the ROM  320 , the HDD  330 , and the RAM  340  are interconnected through a bus  350 . 
     In the ROM  320 , a basic program such as an OS is stored. In the HDD  330 , drawing program  330   a , which realizes the same functions as those of the recording unit, the measurement unit, the drawing unit, the display control unit, the determination unit, and the like illustrated in the above-described embodiments is stored in advance. The drawing program  330   a  may be appropriately separated. In addition, in the HDD  330 , first CAD data, second CAD data, a measurement point table, a connection table, image data, and the like are disposed. The first CAD data, the second CAD data, the measurement point table, the connection table, and the image data correspond to the first CAD data  13   a , the second CAD data  13   b , the measurement point table  13   c , the connection tables  13   d ,  33   d , and  43   d , and the image data  13   e  described above. 
     Then, the CPU  310  reads the drawing program  330   a  from the HDD  330  and executes the drawing program  330   a.    
     Then, the CPU  310  reads the first CAD data, the second CAD data, the measurement point table, the connection table, the image data, and the like and stores the data and tables in the RAM  340 . In addition, the CPU  310  executes the drawing program  330   a  using the first CAD data, the second CAD data, the measurement point table, the connection table, the image data, and the like that are stored in the RAM  340 . it is not necessary to store all data in the RAM  340 , but only data used for the processing may be stored in the RAM  340 . 
     Moreover, it is not necessary to store the above-mentioned drawing program in the HDD  330  from the initial stage. 
     For example, the program is stored in a “portable physical medium” such as a flexible disc (FD), a CD-ROM, a DVD disc, a magneto-optical disk, or an IC card that is inserted into the computer  300 . Then, the computer  300  may be configured to read the program from the portable physical medium and execute the program. 
     Furthermore, the program is stored in “another computer (or a server)” that is connected to the computer  300  through a public circuit, the internet, a LAN, a WAN, or the like. Then, the computer  300  may be configured to read the program from another computer and execute the program. 
     According to one aspect, the appearance of a voltage drop in the laminated circuit board can be perceived in an easy manner. 
     All examples and conditional language recited herein are intended for pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.