JPH0520387A - Circuit design supporting system - Google Patents

Abstract

PURPOSE:To support a check simplification design performed by a designer by expressing the possibility of check of the planning circuit in the logic circuit design using a circuit design supporting device. CONSTITUTION:A circuit information inputted through an I/O device 12 is processed at a circuit connection information processing part 17, then the possibility of check of the circuit which is preparing in a check possibility measure evaluation part 18 is calculated based on the check possibility measure in a primitive library 13. The check difficulty part in the circuit is decided by a check difficulty part judgment part 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit design support device for designing a logic circuit.

[0002]

2. Description of the Related Art In recent years, with the progress of semiconductor technology, the scale and complexity of logic circuits have advanced, and a great deal of man-hours and time are required for the design thereof. Generally, relatively small and medium scale circuits are being designed by automatic logic synthesis. But a large circuit,
In particular, for circuits such as microprocessors that require high integration and high-speed operation, the circuit designer uses a computer-aided design support device to design some or most of them manually. It is the present situation (for example, IPSJ Research Report 89-DA-47, 47-3-1).

Further, with this problem, the cost required for the inspection for ensuring the reliability of the product and the generation of the inspection input is also increasing and becoming difficult. In order to easily perform inspection and inspection input generation, some circuits are changed or added to make the inspection easy.

[0004]

However, if a high-integration and high-speed circuit can be realized by manually designing without using the automatic logic synthesis system, on the other hand, since no consideration is given to product inspection, that circuit is not considered. Inspection and inspection input generation become difficult. Also, in this case, since the designer performs design with only the limit, simple circuit addition or modification to facilitate inspection after design cannot satisfy the specifications such as circuit area and delay. It is difficult to make it.

The present invention is to solve the above-mentioned problems and is an interactive type in which the inspectability of a circuit under design can be evaluated and the designer himself / herself can design for facilitating the inspection. It is an object of the present invention to provide a circuit design support device.

[0006]

A circuit design support apparatus according to the present invention adds a testability scale as information held by a basic element which is a constituent element of a circuit required for design, and based on the scale It has a function to evaluate the inspectability of the circuit and clarify the difficult-to-inspect part based on the evaluation result.

[0007]

The circuit design support apparatus of the present invention sequentially evaluates the inspectability of the circuit designed by using this apparatus during designing, and based on the evaluation result, the inspection difficult part in the circuit is determined. Detect and
It is intended to inform the user (designer) of the part, and to support the inspection facilitation design automatically or by the user. In addition, the circuit obtained as a result has a high testability and becomes a circuit in which the designer understands the testability of the circuit.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an interactive logic circuit design support device according to an embodiment of the present invention.

In FIG. 1, the processing unit 11 includes an input / output control unit 16 for communicating with a user, a circuit connection information processing unit 17 for processing information such as circuit connection relations and logical functions and characteristics. An inspectability scale evaluation unit 18 for calculating an inspectability scale, and an inspection difficulty unit determination unit 19 for determining a portion in the circuit that is difficult to inspect. 12 is a user (designer)
It is an input / output device including a graphic display, a keyboard, a mouse, and the like for interacting with the device processing unit 11. Reference numeral 13 denotes a basic element (hereinafter referred to as a primitive, for example, as shown in FIG. 2) necessary for a user to design a logic circuit.
No. 21) is stored in the primitive library. Reference numeral 14 is a storage device for storing the designed circuit. 15 is a value (threshold value) representing the standard of inspectability,
This is a test facilitation design circuit library in which circuits for test facilitation design are stored.

The primitives stored in the primitive library 13 are added with information such as their logical functions and delay times, as well as an inspectability measure serving as an index showing the ease of inspection.

An outline of the flow of circuit design using this apparatus will be described with reference to FIG. The user designs the circuit through the input / output unit 12. When a user connects a circuit using a primitive in the primitive library 13, the information is processed by the circuit connection information processing unit 17, and at the same time, the testability of the circuit being created is checked by the testability scale of the primitive library 13. It is calculated in the inspectability scale evaluation unit 18 based on the information (steps 1 and 2). Based on the result of the inspectability evaluation, the inspectable part determining unit 19 determines the inspectable part of the circuit (step 3), and the inspectability reference (threshold value) shown in the inspectable design circuit library 15 is used. If it exceeds the limit, point out to the user. At this time, if the user instructs to automatically perform the design for facilitating the inspection, a part of the circuit is changed or added by the circuit connection information processing unit 17 based on the facilitating the design circuit library 15 (step 4.5). If the user does not want to perform the inspection facilitation design or the circuit change, the design is continued as it is (step 6). These operations are repeated until the circuit is completed.

The testability indicates the testability of how easily the test can be carried out. Generally, it can be considered that the cost required for the test is low if the testability is high. The testability scale is a method of expressing testability by quantity. Goldst is a typical testability measure.
Ein scale (Eye Triple E Transaction, Circuits and Systems 26-9 (1979), pages 685 to 693
Page, (IEEE Trans. Circuits and Systems, Vol.CAS-26,
No.9, pp685-693)), but here, for simplification, the following two scales are considered as testability scales.

1. Controllability of the signal line N Cost required when setting the logical value 1 or 0 to the signal line N.

2. Observability of signal line N Cost required to propagate the value of signal line N to an external output.

The calculation methods of the above two inspectability measures are defined as follows. (Calculation method 1) (1) The controllability of the external input is set to 1, and the observability of the external output is set to 0. (2) Controllability of the input line of the basic element is 0, observability is 1
And (3) Controllability of output line of basic element is 1, observability is 0
And

FIG. 2 shows an example of the inspectibility measure of the primitive. Reference numeral 21 is a basic element having input lines 22 and 23 and an output line 24. Value added to each signal line 25, 2
6 and 27 indicate (controllability cost, observability cost). These values are the primitive library 13 in FIG.
Are assigned to each of the primitives.

(Calculation Method 2) (1) The controllability of the input line of a partial circuit formed by connecting a plurality of basic elements or partial circuits is set to 0,
The observability is the sum of the observability of the basic elements or the partial circuits that form the path to the output line of the partial circuit. If there are multiple routes, use the minimum value of the sum of the routes. (2) The observability of an output line of a partial circuit formed by connecting a plurality of basic elements or partial circuits is set to 0,
The controllability is defined as the sum of the controllability of the basic elements or the partial circuits forming the path to the input line of the partial circuit. If there are multiple routes, use the minimum value of the sum of the routes.

According to these calculation methods, the testability of the circuit is calculated in the processing section 11 in FIG. An example thereof is shown in FIG.

FIG. 4 shows an operation example of this apparatus. Depending on the user, the primitive libraries 13 to 2 in FIG.
The primitives 41 and 42 are taken out, and the signal line 43
Then, the circuit composed of these two primitives is made into one partial circuit 44, and the inspectability of the input lines 45, 46, 47 and the output line 48 of this partial circuit 44 is inspectable. (Fig. 1-18).

In FIG. 5, the partial circuit 53 formed by connecting the primitive 52 to the partial circuit 51 is also processed in the same manner as the connection between the primitives shown in FIG.

The larger the controllability value and the observability value (cost) thus obtained, the more difficult the inspection is.

In the present embodiment, the controllability and observability threshold values stored in the testability design circuit library (FIGS. 1-15) are all set to 10. In FIG. 6, reference numerals 61 and 62 denote partial circuits created by the user. The numerical value added to each signal line represents (controllability cost, observability cost) as described above. FIG. 7 shows a circuit obtained by connecting the output line 63 of the partial circuit 61 and the input line 64 of the partial circuit 62. The inspectability of each signal line is newly calculated and becomes the value shown in each. At this time, the observability of the input lines 73 and 74 is 12 and 11, respectively, both of which exceed the threshold value 10.
4 is low in observability.
9). If the user instructs the automatic change of the inspection facilitation, the inspection facilitation design library (see FIG.
-15) based on the information of (1) circuit connection information processing unit (Fig. 1-1
7), the branch signal line 86 is added to the signal line 85 on the common output path of the input lines 83 and 84 as shown in FIG. 8 to increase the observability of the input lines 83 and 84 and facilitate inspection. The design is done.

Further, the input line 87 of the circuit shown in FIG.
The circuit of FIG. 10 is obtained by connecting the output line 92 of the partial circuit 91 shown in FIG. At this time, the controllability of the output line 105 becomes 11 and exceeds the threshold value 10. Therefore, it is shown that the controllability of the output line 105 is low as in the case of the observability described above. On the other hand, if the user selects the automatic change, as shown in FIG. 11, a basic element having a highly controllable input is inserted in the signal line 114 located on one of the input paths of the output line 115, The controllability of the output line 115 is enhanced, and a design for facilitating inspection is performed.

In this embodiment, only the automatic change for facilitating the inspection is shown as a specific example. However, as shown in the flow chart of FIG. The method of substituting parts is also effective.

[0025]

As described above, according to the circuit design support apparatus of the present invention, the interactive circuit design support apparatus has the inspectability scale evaluation section and the inspection difficulty section determination section in the processing section of the circuit design support apparatus. It is possible to proceed with the design while grasping the inspectability of the circuit, and it is possible to easily perform the inspection facilitation design. Also, unlike the method of evaluating the inspectability of the circuit after the circuit design and changing or adding the circuit for facilitating the inspection, it is possible to obtain a circuit that satisfies the intention of the designer, the constraints of the design space and the specifications in a relatively short time. be able to. As a result, the inspection cost for the manufactured circuit is reduced and the reliability is improved, which is extremely advantageous in practical use.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an interactive logic circuit design support device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a basic element (primitive) and its inspectibility measure.

FIG. 3 is a diagram showing an example of calculation of an inspectability measure.

FIG. 4 is an operation explanatory diagram for a circuit composed of two basic elements in the embodiment.

FIG. 5 is an operation explanatory diagram for a circuit including one partial circuit and one basic element in the embodiment.

FIG. 6 is a partial circuit diagram.

FIG. 7 is a diagram showing a display when the observability exceeds a threshold value.

FIG. 8 is a diagram showing an example of a design for facilitating inspection.

FIG. 9 is a partial circuit diagram.

FIG. 10 is a diagram showing a display when controllability exceeds a threshold value.

FIG. 11 is a diagram showing an example of a design for facilitating inspection.

FIG. 12 is a flow chart of circuit design using this device.

[Explanation of symbols]

 Reference Signs List 11 processing device 12 input / output device 13 primitive (basic element) / library 14 storage device 15 test facilitation design circuit library 16 input / output control unit 17 circuit connection information processing unit 18 testability scale evaluation unit 19 test difficult portion determination unit

Claims (1)

Claim: What is claimed is: 1. An interactive circuit design support device in which a device for inputting and outputting the connection information is connected to a device for processing connection information of basic devices that form a circuit. An inspectability evaluation unit that calculates the inspectability of the circuit based on the inspectability measure added to the inspectability evaluation unit, and an inspection difficulty unit determination unit that determines the inspection difficulty unit based on the result of the inspection capability evaluation unit. An interactive circuit design support device having.