Computer-Aided Design of Systems

This invention relates to computer aided design and more particularly, to controlling the entire design, for example, from engineering concepts through physical design and tests, to schematics, final layout and manufacturing specifications.

Considerable emphasis has been placed on computerized design. Computer-aided design has been used, for example, to lay out integrated circuits and VLSI chips. Computer-aided techniques have also been used to translate logic diagrams into electrical schematics and to lay out printed circuit boards from electrical schematics. Examples of such computer-aided electronic circuit design are shown in U.S. Pat. Nos. 4,377,849-Finger, et al "MACRO ASSEMBLER PROCESS FOR AUTOMATED CIRCUIT DESIGN"; and 3,622,762-Dyer, et al "CIRCUIT DESIGN BY AN AUTOMATED DATA PROCESSING MACHINE".

Typically, in the prior art, computer-aided techniques have been used to generate electrical schematic diagrams and another computer-aided process has been used to simulate the operation of the circuit and another, to generate physical layouts of the circuit board. Then, a simulation is made of the operation of the electrical and mechanical circuits and the two are compared. Differences are adjusted, finally producing an electrical and mechanical layout of the circuit which satisfies the designer's requirements. Documentation representing the electrical schematic and the physical layout is produced and used in the manufacture of the circuit boards. One of the principal problems in this prior art approach is that when changes are made in either the physical layout of the circuit or in the electrical schematic, these changes are not necessarily accurately reflected in the documentation for all parts of the electronic circuits.

It is desirable to bind the logical model, electrical circuit layout and mechanical design in the computer program so that changes in any one of them are reflected in changes in all of them and in their documentation. This has not been done in the past because of the complexity of programming required to perform all of the operations on one single data base.

Workers in the field have recognized that object-oriented programming will reduce the complexity of coding. For example, Xerox Corporation developed a computer-aided system referred to as "Small Talk". But the speed of the system was not sufficiently high for the design automation process. It was not a computational efficient program.

It is an object of the present invention to provide a computer-aided design system with object-oriented coding which is extremely fast.

It is another object of the present invention to increase the productivity of designers by providing a tool which will produce complete designs.

It is another object of the present invention to reduce errors and produce design continuity.

In accordance with the present invention, a graphical computer-performed method of designing a system includes data objects programming in which a plurality of manipulative programs are linked to each data record representing a primitive element in the system. The manipulative programs perform all of the operations necessary for the design process. The data records are linked in a hierarchy which graphically represents the design. A series of high order, very simple, commands operate selected manipulative programs in the hierarchy. Because the high order commands are very simple, and because the manipulative programs are linked to the data records in the hierarchy, it is not necessary to change each of the high order commands when a change is made in the data base representing the design. Changes in the design can be made easily and quickly without extensive changes in the programming.

Change and revision control are much easier. The manipulative programs linked to a particular data record contain the only coding which directly manipulate that data record. The ability to configure the data base during run-time is easier. Another advantage of the invention is complexity management. It allows integration of cross-links which permit the use of a logical model, which controls the complete design. In the case of electronic design, an electrical circuit layout is generated by the computer and a mechanical design is generated, both directly from the logical model. Documentation is produced from the logical model, the circuit layout and the mechanical layout. The logical mode, electrical circuit layout and mechanical design are bound in the computer so that changes in any one of them will be reflected in changes in all of them and in their documentation.

In one application, the logical model produced by the computer-aided process of the present invention represents devices such as AND gates and resistors, and their connections. It does not represent unit designations or pin numbers. From the logical model, an electrical circuit layout is generated which has unit designations and pin numbers. The electrical circuit layout defines trace widths and attributes such as the capacitance of traces. From this, a mechanical design is produced which models the packaging, card cages, structures and assemblies. Each of the logical models, circuit layout, and physical design, may be viewed, manipulated, and operated upon. The logical model is used to control the basic circuit designs, the layout controls, VLSI and printed circuit board design. The mechanical design controls the packaging and assembly of the product.

The foregoing and other objects, features and advantages of the invention will be better understood from the following more detailed description and appended claims.

FIG. 1 depicts a computer graphics system used in a computer-aided design and/or engineering system;

FIG. 2 depicts the manner in which the prior art operates;

FIG. 3 depicts the advantages of the present invention;

FIG. 4 depicts a simple logical circuit, and FIG. 5 depicts a revision of it;

FIG. 6 depicts the manner in which most prior art systems retrieve graphics from a data base;

FIG. 7 depicts a prior art object oriented programming technique;

FIG. 8 depicts the object-oriented computer graphics system of the present invention;

FIG. 8A depicts a data object in accordance with the invention;

FIG. 8B depicts the manner in which a data object performs a display.

FIG. 1 depicts a computer graphics system for computer aided design wherein a work station computer 11 responds to inputs from a keyboard 12 and a digitizing device such as a light pen, tablet, or mouse 13, displays designs on the graphical display device 14. Programs and a data base are stored in the mass storage 15 which is typically magnetic disk storage. In a computer graphics aided design, shapes or lines are displayed on the graphical display device 14. As a simple example, the line connecting the points x,y and x.sub.1,y.sub.1 is shown. Typically, a data base object is brought from mass storage to computer 11 as a whole. Multiple programs are added to the base structure. A message like "DISPLAY" sent to the structure results in a graphic presentation on the display 14. Inputs from the keyboard 12 and digitizing device 13 are sent by messages back to the data base structure resulting in changes in data base. The whole data structure is cleaned up and stored back in mass storage 15.

FIG. 2 depicts a typical prior art technique for designing an electrical circuit with computer graphic techniques. An electrical schematic is generated and from this a net list is extracted. From the net list, a mechanical layout is generated. Simulations of the operating characteristics of the electrical schematic are performed to verify the schematic. Likewise, simulation is performed on the mechanical layout. The simulations are compared to verify them and adjustments are made.

Summarizing, the following steps are performed:

(1) The schematic is drawn as a disjointed line;

(2) Net list is extracted and sent to simulation;

(3) Simulation verifies design;

(4) Net list is sent to layout;

(5) Manual and/or automatic layout occurs;

(6) Net list is extracted from layout;

(7) Simulation on layout is performed;

(8) Net lists from schematic and layout are compared;

(9) Simulations are manually compared.

In accordance with the present invention, designs such as an electrical circuit are produced as depicted in FIG. 3, wherein all of the programs for generating the logical model, the electrical and mechanical layouts are generated from the same data base. The operation of all of the circuits is simulated on the same data base and documentation is produced from the same data base.

The operation in accordance with the present invention is summarized as follows:

(1) The logical layout and mechanical models are stored in the same data base with cross-linkage.

(2) The designer generates the logical model;

(3) Simulation verifies the logical model. No extraction is necessary. The simulation works directly from the logical model.

(4) The logical model directs the layout and does not allow wrong connections.

(5) The layout directs the mechanical model.

(6) Information like unit reference assignment is only stored in one place, the layout.

(7) Documentation is generated by taking points of view of the logical model and referencing information in the layout model to form a schematic.

As an example of the problems encountered in prior art computer-aided design of electrical circuits, consider FIGS. 4 and 5. Two AND circuits A and B are connected to an OR circuit. This is designed graphically by selecting the primitive shapes of the AND gates and displaying them. The data base representing the components is designated A. Then wires are added by a data base designated B, and connections are added by a data base designated C. After graphical entry of the electrical circuit, a net list is extracted. (This is a list of all pins on each component and the connections pin to pin.) The net list is typically an input to a simulation program which generates the output waveforms. Problems are discovered which have to be corrected in the graphical schematics. The circuit designer continues this procedure until an entire circuit is designed. A major problem arises when he wants to make changes in the circuit such as depicted in FIG. 5, wherein an inverter is added and the OR gate C is rotated by 90.degree.. The designer must graphically change the schematic, re-extract the entire net list, and re-do the simulation.

FIG. 6 depicts a prior art computer graphics program which includes commands such as WRITE, READ, DISPLAY, ERASE, and other commands. A data base includes a plurality of records indicated by the circles. For example, the records depicted by the circle A denote the components such as the AND and OR gates in FIG. 4. The records depicted by the circles B and C denote the wires and the connections, respectively. The commands which write and read these data records, display them, erase them, and do other operations, each include code which manipulates a particular data record. That is, each of the commands has a section which deals specifically with the data records A, B, and C. When the programmer wants to make a change to the data base like adding a new class of elements, D, which represents miscellaneous lines, he must change every one of the commands and programs which operate on this new record. When the programmer changes another existing element, like element A, he must go back into the command programs and change every one of them. This is an extensive change. Furthermore, the complexity of managing multiple programs on the same data base is quite high. For example, doing a simulation, or a mechanical layout, using the same data base is so complex that it is generally not done.

Object-oriented programs tend to alleviate the problem. Referring to FIG. 7, object-oriented programs are accessed by commands which are in a character string such as "DISPLAY." For example, consider the manner in which the command "DISPLAY", draws a line between x,y, and x.sub.1,y.sub.1. The character string DISPLAY is parsed. That is, the characters in the string are compared one by one by the object. When the parsing indicates that a DISPLAY command is to be performed, it displays the line segment x,y-x.sub.1,y.sub.1. This is quite time consuming. It is so time consuming that prior art computer graphics systems using object-oriented programming have not been able to provide good interaction.

The present invention as depicted in FIGS. 8, 8A and 8B, allows the use of object-oriented programming which quickly performs graphical operations in access times which produce good interaction. The invention uses a modification of the object-oriented technique, which will be referred to as "data-object". A data-object is a data record that has a link to its manipulative programs. The manipulative programs are the only programs which directly manipulate the data records. A message is sent to the data-object via a procedure call through the link stored in the record. This allows the interpretation of a message to be as fast as a procedure call.

Referring to FIG. 8A, in order to reduce storage and increase speed, the data-object 20 does not contain its link directly, but its parent data-object 21 stores it. This allows the pointer to be fetched once and used with each data record, since all common data records are stored in a list under their common data-object parent. But each data record and its manipulative programs, indicated at 22, still function as a data-object.

FIG. 8B depicts the manner in which a data object performs the task of displaying the line x,y-x.sub.1,y.sub.1. The direct link from the parent data-object 23 to the manipulative program 24 performs the display procedure just as parsing the "DISPLAY" message carried out this procedure in the prior art.

FIG. 8 shows the data objects of the present invention configured in a data object system. Stored data records 25-29 each represent a primitive element in the system. Manipulative programs 30-34 are respectively linked to the data records 25-29. Each set of manipulative programs performs the necessary operation on the primitive elements for the design of the system.

For example, the set of programs 30 denoted PRMOPR perform operations on the primitive shapes of circuits in the electronics circuit, such as the AND and OR gates of FIG. 4. These programs include the capability to read, write, display, erase, move, rotate, highlight, and perform other operations on the primitive elements which in this case are components. In the exemplary embodiment, there are twenty-five manipulative programs linked to each record in the data base.

The set of manipulative programs 32 is denoted PINOPR. PINOPR includes twenty-five manipulative programs for performing all operations on the data records representing the pins. The programs 31 are denoted WIROPR. This includes twenty-five manipulative programs for performing all operations on the data records designating the wire connectors. Each small program represents a single message.

Note that a data-object might be a record which has a structure of other data-objects underneath it. Such a data-object includes a data record 25 and manipulative program 30 in FIG. 8. It is the responsibility of this data-object to pass on the messages it received to the lower data-object structure.

In accordance with the present invention, the data records in the data base are linked so that the manipulative programs are performed in a sequence set up by the designer and without the need for parsing, or interpreting the character string of a command. The low level data records 26-29 are linked in a hierarchy and these in turn are linked to the medium level record 29. The medium level manipulative programs 34 perform operations on an entire page of schematics, for example. The designer has the capability to extend the hierarchical tree of linked data records so that an entire system is represented.

Access to the tree of data records is through high order commands such as those indicated at 35-38. These are retrieved from file 39 and perform operations, such as DISPLAY or WRITE, on the entire design which the designer has laid out. Note that only these high level programs must be parsed to interpret the character string to determine what operation is to be performed. Once the character string has been parsed and the operation to be performed has been determined, access is provided to the highest level program in the data base. Then, the program proceeds by links from one pointer to another of the records in the data base. Only the high level commands, such as 35-38, require time for the interpretation of character strings. After this initial interpretation, a program, such as DISPLAY, proceeds quickly by means of the linked pointers.

A menu/configuration file 40, 41 sets up a menu for a particular application. This file also contains a blue-print of the data-object structure required for this application. High-level programs refer to this blue-print to set up the initial data base structure. The menus, when selected, send high level messsages to the high-level procedures.

Changes can easily be made in the system by just changing the configuration file. Once the high level programs, configuration file and data records are set up with links to their associated manipulative programs, most of this programming will not be changed when a change is made in the system. The high and medium level programs have nothing which is unique to a particular data record. Data records can be changed without changing the high and medium level programs. These programs perform an operation dependent only on the links between pointers.

FIG. 8 contrasts the invention with the problem encountered in the prior art as shown in FIG. 6. When a new class of data object, 28, designated "D", are added to the structure, the command programs 35-38 need not change, since they do not directly manipulate the data base structure. This new data-object, once added to the structure, will receive all the messages from its parent data-object above. Now a "DISPLAY" message sent to the data structure will display "D", because D was added with its manipulative programs 33 attached. Also, note that changes to element "A" only affect manipulative programs attached to "A" and not to any of the systems command procedures.

The Appendices include exemplary listings showing the manner in which the invention was implemented using the language MAINSAIL, by XYDAC. As with all computer programs, they must be written for the particular hardware and carefully debugged. The Appendices are useful examples of one implementation.

Appendix I contains listings of exemplary low level programs. Simple display, erase, move and duplicate routines are given first. Appendix I also contains exemplary listings for PINOPR, CMPOPR, and WIROPR, which were referred to in conjunction with FIG. 8. These manipulative programs perform the basic operations on data records which represent pins in the case of PINOPR, basic components in the case of CMPOPR, and wires for program WIROPR.

Appendix II contains medium level programs. Note that these are much simpler than the low level programs. A particular program included in the Appendix is a procedure for displaying all of the logic elements in a group, for moving a group of records, and for copying a group of records.

Appendix III contains high level programs. The particular programs include a program for moving records, copying records and deleting records. Note the simplicity of the high level programs. This is an important advantage of the invention in that changes in the system require minimal changes in the high and medium level programs. Most of the changes can be made at one place in the low level programs.

Appendix IV is an example of a configuration file which links the data records in the design of a particular circuit.

While a particular embodiment of the invention has been shown and described, various modifications are within the true spirit and scope of the invention. The appended claims are, therefore, intended to cover all such modifications. ##SPC1##