JPS6018946B2 - Logic circuit output test equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to logic circuit output tests, especially when the logic function device under test constitutes logic with a difference between two signals such as bipolar. This is related to the test bag to be judged.

Conventionally, the logic function device l, which is the test object, is T shown in FIG.
It had a unipolar output as typified by a TL logic circuit.

Therefore, the logic judgment for the output is, for example, a high level of 2.4 volts or more is considered to be logic "1", and 0.4
It has been sufficient to determine whether the voltage is above a predetermined high potential reference voltage or below a predetermined low potential reference voltage, such that a voltage below volt is a logic "0". However, recently, as a measure to make the logical function Ryoreki, which is the object under test, noise-resistant when applied to communication lines, etc., many products have bipolar output. In the logic function device having the bipolar output, for example, if the bipolar outputs are A and B as shown in FIG. When logic
1", and when it is negative, it is logic "0". Therefore, the logic judgment for the latter polarity output depends on whether the differential voltage is positive or negative. In the case of a positive differential voltage, the value of the positive differential voltage and a predetermined positive reference voltage are determined. Also, in the case of a negative differential voltage, compare the value of the negative differential voltage with a predetermined negative reference voltage to determine whether the value of the differential voltage is within the respective reference voltage range. I have to decide whether. The present invention aims to solve this problem by providing a testing device with a polarity discrimination section and a voltage determination section, which checks the validity of magnetism and automatically switches the circuit according to the determined polarity. It is an object of the present invention to provide a logic circuit output testing device capable of testing the logic output of a logic function device having bipolar outputs by comparing the voltage difference in polarity with a predetermined reference voltage. Therefore, the logic circuit output test device of the present invention tests whether the multiple signal voltage output from the logic function device under test is output based on a predetermined logic or not. In the output test equipment,
a differential amplifier for extracting a voltage difference between the polarized signal voltages output from the test object; a sacrificial discrimination section for determining the polarity of the voltage difference between the signal voltages extracted by the differential amplifier; a first voltage comparison circuit that compares the differential voltage with a positive reference voltage when the polarity determined by the polarity discrimination section is positive; and a first voltage comparison circuit that compares the differential voltage with a positive reference voltage when the polarity determined by the polarity discrimination section is negative; and a negative voltage, an output logic comparison section for confirming the validity of the polarity determination result by the polarity discrimination section, and an output logic comparison circuit for comparing the output of the output logic comparison section with the first and second voltages. The present invention is characterized in that it includes an output logic function determining element that checks the operation of the logic function device based on the output of the voltage comparison circuit. This will be explained below with reference to the drawings. FIG. 2 shows the circuit configuration of an embodiment of the logic circuit output testing device according to the present invention, and FIG.
A time chart illustrating the operation of the illustrated embodiment circuit is shown.

In FIG. 2, 1 is a data processing device, 2 is a logical function device under test, 3 is a terminating resistor that prevents undesired reflections, 4 is a test equipment, 5 is a differential amplifier, 6 is a sacrifice discrimination section, 7 is a voltage determination section, 8 is a first voltage comparison circuit,
9 is an AND element, 10 is a second voltage comparison circuit, 11 is an AND element, 12 is a NOT element, 13 is an OR element, 14 is an output logic comparison section, 15 is an output logic function determination circuit, 16 is an output expected logic value It represents a signal given from the data processing unit 1. A predetermined pattern of signals is supplied from the data processing device 1 to a logical functional device consisting of a circuit or an element to be tested, and the inverted output signal IN+, which is a bipolar output signal, is output from the device under test 2. It outputs a non-inverted output signal IN-.

A terminating resistor 3 is provided at the input device of the test apparatus 4 of the present invention to prevent the output of the test object 2 from causing undesired reflections. The inverted output signal IN+ from the device under test 2 which has passed through the termination resistor 3 is inputted as a voltage VA, and the non-inverted output signal m- is inputted as a voltage yB to the differential amplifier 5 of the test apparatus 4. The differential amplifier 5 calculates the difference between the input voltage VA and voltage VB and outputs a difference voltage VC. The beauty cyst pressure yC outputted from the differential amplifier 5 is input to the polarity discriminator 6 and the voltage determination section 7, and the polarity discriminator 6 receives the differential voltage V.
When C is positive, logic "1" is output, and when C is negative, logic "0" is output as logic output VD. On the other hand, the differential voltage VC input to the voltage determination section 7 is input to the first voltage comparison circuit 8 and the second fin pressure comparison circuit 10 of the voltage determination section 7, and is determined by the polarity discrimination section 6. When the polarity is determined to be positive, the first voltage comparison circuit 8 converts the differential voltage VC into the positive reference voltage V+, and when the polarity discrimination section 6 determines the polarity to be negative, the differential voltage VC is converted into the second voltage. It is compared with a negative reference voltage V- in a voltage comparison circuit 10. The voltage determination unit 7 compares the differential voltage VC with the positive reference voltage V+ or the negative reference voltage V- as described above, and if it is determined that it is within the reference voltage value, it also determines logic "1" as being outside the reference voltage value. In this case, logic "0" is output as the voltage determination section output VF. The logic output VD of the polarity determination section 6 is input to the output logic comparison section 14 in order to confirm the validity of the polarity determination result. In the output logic comparison section 14, the data processing device 1
A match is made with the expected output logic value signal 16 inputted from the output logic comparator VE. The output logic comparator output VE obtained in this way
and the voltage judgment unit output VF are input to the output logic function judgment circuit 15, and the output logic comparison unit output VE is further logically ANDed in the output logic function judgment circuit 15.
If the output of the output logic comparator and the voltage judgment unit output VF are both logic “1”, the logic is “1”, and the output logic comparison unit output VE or the voltage judgment unit output V
If either output of F is logic "0" or both are logic "0", logic "0" is outputted as output logic function determination circuit output VG. Therefore, when the output VG of the output logic function determination circuit 15 is logic "1", it is determined that the test object 2 is operating with normal function, and the output VG
When is logical "0", it can be determined that the test object 2 has a fault. FIG. 3 is a time chart illustrating the operation of the embodiment circuit shown in FIG.

Test 1 is for a test object with positive polarity and normal function.
Test 2 is for a test object with negative polarity normal function, and the output logic function judgment circuit output V in the test equipment
Each G becomes logic "1" and is determined to be normal.

Tests 3 and 4 are for a test object with a differential voltage failure, and the polarity matches the output expected logical value of positive polarity and negative polarity, respectively, but the differential voltage VC does not reach the reference voltage value. Therefore, the output VF of the voltage determination section is respectively logic "OJ", and naturally the output VG of the output logic function determination element is also logic "0", which determines that there is a failure. Tests 5 and 6 are for the test object with a polarity fault, and the value of the differential voltage VC has reached the reference voltage, so the voltage judgment section output VF is logic "1", but the output logic comparison section Therefore, the output logic comparator output VE is both logic "0", and naturally the output logic function judgment element output VG is also logic "OJ", and it is determined that there is a failure. As explained above, according to the logic circuit output testing device of the present invention, the voltage is determined by comparing the positive and negative reference voltages based on the polarity discrimination result, and the validity of the polarity discrimination result is reconfirmed. That's what I do.

Therefore, testing of bipolar test objects can be performed easily and reliably.

[Brief explanation of the drawing]

Figure 1A is an example of a conventional test object represented by a TTL logic circuit, Figure 1B is an example of a logic functional device with bipolarity,
FIG. 2 shows a circuit configuration of an embodiment of the logic circuit output testing apparatus according to the present invention, and FIG. 3 shows a time chart illustrating the operation of the embodiment circuit shown in FIG. In the figure, 1 is a data processing device (CPU), 2 is a test object,
4 is a test device of the present invention, 5 is a differential amplifier, 6 is a sacrificial discrimination section, 8 is a first voltage comparison circuit, 10 is a second voltage comparison circuit, 14 is an output logic comparison section, and 15 is an output logic function Judgment circuit, 16 is an output expected logical value signal, V+ is a positive reference voltage, V
- represents a negative reference voltage. Yaa Red A〕 Boo Kyou (Mo) Complete Z Figure 73 Kyou

Claims (1)

[Claims] 1. In a logic circuit output test device that tests whether a bipolar signal voltage output from a logic function device that is a test object is output based on a predetermined logic or not,
A differential amplifier for extracting the voltage difference between the bipolar signal voltages output from the above-mentioned test object, and a polarity discrimination for determining the polarity of the voltage difference between the signal voltages extracted by the differential amplifier. a first unit that compares the differential voltage with a positive reference voltage when the polarity determined by the polarity discriminator is positive;
a voltage comparison circuit, a second voltage comparison circuit for comparing the difference voltage with a negative voltage when the polarity determined by the polarity discrimination section is negative, and a second voltage comparison circuit for confirming the validity of the polarity determination result by the polarity discrimination section. an output logic comparison section, and an output logic function determination circuit for checking the operation of the logic function device based on the output of the output logic comparison section and the outputs of the first and second voltage comparison circuits. A logic circuit output test device featuring the following features.