JPH056926A - Input/output circuit of large-scale integrated circuit - Google Patents

Abstract

PURPOSE:To simply and surely perform a leak test at the part of a terminal by a method wherein circuits performing an operation in a mode equivalent to that of individual circuits are added respectively and control-signal terminals which control a constituent circuit so as to perform a prescribed operation only in the test and measuring operation of the constituent circuit are provided. CONSTITUTION:A chip 15 for a large-scale integrated circuit is constituted in such a way that circuits 17, 20 performing an operation in a mode equivalent to that of individual circuits are added respectively to an input circuit 16 and an output circuit 19 which are designated by a user. It is provided with control- signal terminals 18, 21 which control a constituent circuit so as to perform a prescribed operation only when the constituent circuit is tested and measured. When the constitution of an internal circuit 3, the input circuit 16 and the output circuit 19 is designated, the added circuits 17, 20 are kept added. When the operation of the chip 15 is tested, control signals are applied from the terminals 18, 21, the added circuits 17, 20 are operated jointly with the input circuit 16 and the output circuit 19 and perform an operation in a mode equivalent to that of the input circuit 16 and the output circuit 19. Thereby, the operating test of the chip can simply and surely be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input / output circuit of a large scale integrated circuit. In recent years, with the improvement of technology in integrated circuits,
The miniaturization and increase in circuit scale have become remarkable, making it difficult to test terminals and screen products. Therefore, it has been desired to develop a technique that facilitates the test of the terminal portion of the input / output circuit of the large scale integrated circuit.

[0002]

2. Description of the Related Art In an individual circuit that constitutes a large scale integrated circuit, only the output circuit portion is shown in FIG. In FIG. 8, 1 and 2 are MOS type FETs, 3 is an internal circuit, 4 is an output data terminal from the internal circuit, 5 is an output terminal of the output circuit, 6 is a power supply, 7 is ground, and 8 and 9 are inverters. . In the circuit shown in FIG. 5, the output data from the internal circuit 3 is input from the terminal 4, the FETs 1 and 2 are alternately turned on and off via the inverters 8 and 9, and the output terminal 5
Has obtained the output of "H" or "L". Since the power source 6 is a positive voltage source, the FET1 is a P type, and the FET2 is an N type,
Corresponding to "H" and "L" of data from the internal circuit 3, F
ET1 and ET2 turn on and off. And FET1 is on,
When the FET 2 is off, the terminal 5 outputs "H". F
When ET1 is off and FET2 is on, the terminal 5 outputs "L". This turned-on FET1 acts as a kind of huge leak, and the output terminal 5 cannot measure the leak current. When measuring only the leak current in this circuit, it is necessary to create a state in which the FET2 is also off.

Next, FIG. 9 is a diagram showing a circuit on the input side with respect to the internal circuit. In FIG. 9, 3 is an internal circuit, 10 is a signal input terminal, 11 and 12 are MOS type FETs, 13 is an inverter, and 14 is a data application terminal to the internal circuit. In FIG. 9, when both FETs 11 and 12 are turned off,
The applied signal to the input terminal 10 is transmitted to the internal circuit 3 via the terminal 14, but in the state without the applied signal, the terminal 10
Becomes indefinite and a through current flows through the inverter 13. That state is called floating. In order to avoid the floating state and fix the level, a pull-up resistor may be provided between the terminal 10 and the power supply, and conversely the terminal 10 may be connected.
Screening was performed after connecting a pull-down resistor between the ground and ground.

[0004]

In the circuits shown in FIGS. 8 and 9, the leak current was measured, and an integrated circuit having an abnormally large leak current could not be excluded as a defective product. In FIG. 9, it is necessary to prepare the pull-up / pull-down resistors in the same number as the number of signal input terminals of the circuit. When the number of terminals becomes large, the number of resistance elements surrounding the integrated circuit becomes huge, such as 10,000. Further, since the resistance element is screened at the same time as the large-scale integrated circuit, there is a drawback that it is easily deteriorated, and it takes a long time to attach the resistance element to the measurement substrate.

Since the object of the present invention is to improve the above-mentioned drawbacks and to be a large-scale integrated circuit, a circuit which operates effectively in the equivalent mode for the original purpose of use is connected to simplify and surely perform a leak test or the like at the terminal portion. It is to provide a large-scale integrated circuit that can be effectively used.

[0006]

FIG. 1 is a diagram showing the principle configuration of the present invention. In FIG. 1, 3 is an internal circuit, 15 is a chip of a large-scale integrated circuit, 16 is an input circuit, 17 is an additional circuit that is added to the input circuit and operates in an equivalent mode together with the input circuit, and 18 is a control for the additional circuit 17. A signal terminal, 19 is an output circuit, 20 is an additional circuit that is added to the output circuit and operates in an equivalent mode together with the output circuit, and 21 is a control signal terminal for the additional circuit 20.

In the input / output circuit of the large scale integrated circuit 3,
The present invention has the following configuration. That is, the input circuit 16 and the output circuit 19 designated by the user are configured by adding circuits 17 and 20 that operate in an equivalent mode to the respective circuits, and perform a predetermined operation only when testing and measuring the constituent circuits. The control signal terminals 18 and 21 for controlling the operation are provided.

[0008]

For example, when the user specifies the configuration of the internal circuit 3, the input circuit 16 and the output circuit 19 of the chip 15, the additional circuits 17 and 20 are added in the present invention. When the operation test of the chip 15 is performed, the terminals 18,
A control signal is applied from 21 to cause the additional circuits 17 and 20 to operate in cooperation with the input circuit 16 and the output circuit 19 to operate in an equivalent mode with the input circuit / output circuit. Due to the presence of the additional circuit, the operation test of the chip 15 is simpler than the case where only the input circuit 16 and the output circuit 19 are present.
You can definitely. When the control signal is not applied from the terminals 18 and 21, the operation of the chip 15 via the input circuit 16 and the output circuit 19 remains unchanged.

[0009]

FIG. 2 is a block diagram including an input / output circuit modified with an additional circuit as an embodiment of the present invention. For example, when the circuit group shown in FIG. 2A is designated by the user, the circuit group is changed as shown in FIG. 2B in the present invention. The control signal terminals 22 and 23 are also applied to the input / output common circuit as compared with the terminals 18 and 21 shown in FIG. That is, the designated circuit 24-
In 1,25-1,26-1, 26-1 is a circuit having an input / output function. In the change circuits 24-2, 25-2, 26-2, 26-2 is a circuit having an input / output and pull-up function.

Next, FIG. 3 is a diagram showing a specific configuration of an output circuit with a high impedance function. In FIG. 3, a chain line 27 indicates a circuit having a high impedance output function, and a terminal 21 is a control signal application terminal. In FIG. 3, 1 and 2 are MOS type FETs, 4 is an output data terminal, 28 is a NAND circuit, 29 is a NOR circuit, and 30 is an inverter. When a level “L” is applied from the terminal 21, a logical operation is performed by the NAND circuit 28, the NOR circuit 29, and the inverter 30 and applied to the FETs 1 and 2, so that F
Both ET1 and ET2 are turned off. "H" or "L" is externally applied to the output terminal 5 to measure the leak current with respect to the power source or the ground. In FIG. 3, "H" is applied to terminal 21.
, The inside of the alternate long and short dash line 27 does not affect the FETs 1 and 2, and operates in the same manner as in FIG.

FIG. 4 is a diagram showing a specific configuration of an input circuit with a pull-up circuit and a pull-down circuit. In FIG. 4, a dashed-dotted line 31 indicates a pull-up / pull-down circuit newly provided inside the integrated circuit. In FIG. 4, 32,3
A MOS type FET 3 is turned on / off depending on the presence or absence of a control signal applied from the terminals 34 and 35. The DC potential of the input terminal 10 is switched between the potential of the DC power supply and the ground depending on the presence or absence of the control signal, and the potential level is fixed inside the integrated circuit. Therefore, the leak current is measured in the fixed state.

In this circuit, the FET 32 as a pull-up circuit and the terminal 34 are necessary for the circuit operation, and it is often unnecessary to provide the pull-down circuit.

FIG. 5 is a modification of the circuit shown in FIG. 3, in which the terminal 36 shares the output terminal and the input terminal. 1
A chain line 27 is a circuit having a high impedance output function shown in FIG. 3, and operates in the same manner as in the case of FIG. Figure 5
In 37, reference numeral 37 denotes an inverter, which inverts the input signal and inputs it to the internal circuit from the terminal 14 when the terminal 36 becomes an input terminal.

FIG. 6 is a circuit diagram for explaining a modification in a unit circuit as an integrated circuit. A signal terminal 39 for externally controlling high impedance is further added, and an additional circuit (high impedance output circuit) is provided via a NOR circuit 38 and an inverter. ) Is in control. When the circuit user designs the logic circuit specifications of the circuit enclosed by the broken line, the manufacturer is Noah circuit 3
It is possible to easily and surely measure the leak characteristic when the internal circuit side is viewed from the input / output terminal 36 only by additionally providing 8 and an inverter.

A control terminal can be added in the pull-up / pull-down circuit as well.

FIG. 7 is a main part of an operation flow chart for explaining the contents update of the database in the CAD system for integrated circuits. In FIG. 7, 40 is a conventional database, 41 to 43 are first to third steps, 4
4 shows the updated database. That is, when a user orders a circuit specification from the initial database 40, in the first step 41, the circuit type such as the input side or the output side is determined. Second step 4
In 2, consider an additional circuit of the input / output circuit according to the format judged in step 41. In the third step 43, additional design data for the high impedance or the pull-up / pull-down additional control terminal is stored in the database 44.

[0017]

As described above, according to the present invention, at the time of the operation or attribute test at the input / output terminals, a circuit not explicitly shown to the user is added, and the manufacturing test by the manufacturer is effectively and appropriately shortened. Can be done in time. It is cheap because it is not a measuring device that uses many expensive resistance elements as in the past. Further, the circuit added in the present invention is manufactured from the beginning as an integrated circuit, and when the circuit is not used for a normal purpose, it can be diverted, and at that time, the integrated circuit can be used. The present invention can be realized without increasing the size.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle configuration of the present invention.

FIG. 2 is a diagram illustrating an example of the present invention.

FIG. 3 is a diagram showing a specific configuration of an output circuit with a high impedance function.

FIG. 4 is a diagram showing a specific configuration of an input circuit with a pull-up / pull-down circuit.

5 is a modification of the circuit shown in FIG.

FIG. 6 is a circuit diagram illustrating a modification of a unit circuit.

FIG. 7 is a diagram showing a main part of an operation flowchart of a CAD system.

FIG. 8 is a diagram showing only an output circuit portion of a conventional large-scale integrated circuit.

FIG. 9 is a diagram showing only an input circuit portion of a conventional large-scale integrated circuit.

[Explanation of symbols] 3 Large scale integrated circuit 16 Input circuit specified by user 17 ・ 20 Circuit that operates in similar mode 18 ・ 21 Control signal terminal 19 Output circuit specified by user

Claims (3)

[Claims] 1. An input / output circuit of a large-scale integrated circuit (3), which performs an equivalent mode operation with each circuit for an input circuit (16) and an output circuit (19) designated by a user. Control signal terminals (18) (2) that control the configuration so that the specified operation is performed only when testing and measuring the constituent circuits.
An input / output circuit of a large-scale integrated circuit characterized by comprising 1). 2. The added circuit according to claim 1, which is a circuit for measuring the operation of a large-scale integrated circuit, obtains a high impedance characteristic added to the output circuit side, or a pull-down circuit added to the input circuit side. An input / output circuit for a large-scale integrated circuit characterized by being a pull-up circuit. 3. A CAD system for designing a large scale integrated circuit using a database, wherein the CAD system is designed using a memory storing data for the operation measuring circuit. I / O circuit.