JPH0424667B2 - - Google Patents

Description

Detailed Description of the Invention "Industrial Application Field" This invention relates to the output of a device under test such as a gate logic circuit when the pulse width of the output pulse changes with respect to the input pulse width when an input pulse is applied to the device under test. This invention relates to a pulse width measuring device that measures pulse width.

``Prior Art'' As shown in FIG. 7, a conventional pulse width measuring instrument of this type inputs an input pulse 11 to a device under test 13 such as a gate logic circuit through a drive circuit 12, and measures the value of the device under test 13. supplying the output pulse to the data terminal D of the D-type flip-flop 14;
A strobe pulse is input to the clock terminal CK of the flip-flop 14, and the phase of the strobe pulse is sequentially changed, and the phase difference between the strobe pulse between the point where the Q output of the flip-flop 14 is first inverted and the point where it is next inverted is calculated. , the output pulse width of the device under test 13 was measured.

"Problems to be Solved by the Invention" In this conventional pulse width measuring instrument, the accuracy of the pulse width input from the drive circuit 12 to the device under test 13, the phase setting resolution of the strobe pulse input to the flip-flop 14, the linear The accuracy of pulse width measurement that can be obtained is limited due to large error factors such as

"Means for Solving the Problem" According to the present invention, an output pulse of an edge-triggered monostable multivibrator is supplied to a device under test, and a pulse having a leading edge synchronized with the rise of the output pulse of the device under test, A pulse having a leading edge synchronized with the falling edge is selected by a rising/falling selection circuit and is applied as a trigger pulse to the monostable multivibrator to form an oscillation loop. The oscillation period of the pulse synchronized with the rising edge and the oscillation period of the pulse synchronized with the falling edge are measured with a period measuring device, and the difference between the measured values is calculated to obtain the measured pulse width.

Embodiment FIG. 1 shows the principle of a pulse width measuring device according to the present invention. The output pulse of the edge-triggered monostable multivibrator 15 is supplied to the device under test 13, and the output of the device under test 13 is supplied to one input side of an exclusive OR circuit 16 as a rising/falling selection circuit, and The output of the sum circuit 16 is supplied as a trigger pulse to the monostable multivibrator 15. A selection signal is input from a terminal 17 to the other input side of the exclusive OR circuit 16.

In this configuration, when the selection signal at the terminal 17 is set to a low level, the output pulse from the device under test 13 passes through the exclusive OR circuit 16 as is. The monostable multivibrator 15 is therefore triggered at the leading edge of the passing pulse. Therefore, once a trigger is applied to the monostable multivibrator 15, the monostable multivibrator 15 is repeatedly triggered at the leading edge of the output pulse of the device under test 13, and the pulse oscillation is synchronized with the rising edge of the output pulse. A loop is constructed.

When the selection signal of the terminal 17 is set to high level, the polarity of the output pulse of the device under test 13 is inverted by the exclusive OR circuit 16, so that the output pulse of the device under test 13 is reversed in polarity.
A pulse oscillation loop synchronized with the falling edge of the output pulse No. 3 is constructed. The oscillation period of the pulse synchronized with the rising edge and the oscillation period of the pulse synchronized with the falling edge are each measured by a period measuring device 18,
The difference between the two measurement periods becomes the width of the output pulse.

FIG. 2 shows an embodiment of the invention. It is configured to supply a starting pulse from the terminal 21 to the monostable multivibrator 15 through the OR circuit 22. The output of this monostable multivibrator 15 is supplied to the device under test 13. In this example, the oscillation loop that passes through the device under test 13 and the oscillation loop that does not pass therethrough can be configured to be switched.
The output is selected and outputted. A control signal for the data selector 23 is applied to the data selector 23 from a terminal 24.

The output of the data selector 23 is supplied to a rising/falling selection circuit 25. Rising/falling selection circuit 2
5, the pulse width of the input pulse is expanded by the pulse width expansion circuit 26. That is, the output of the data selector 23 is directly supplied to the OR circuit 27 and also supplied to the OR circuit 27 through the delay circuit 28. The delay circuit 28 has a delay amount shorter than the input pulse width, so the output of the OR circuit 27 has a pulse width expanded by the delay amount of the delay circuit 28.

The output of the OR circuit 27 and its inverted output are supplied to AND circuits 31 and 32, respectively. terminal 17
The selection signal is directly supplied to the AND circuit 31 and also supplied to the AND circuit 32 through the inverting circuit 33. The output of the AND circuit 31 is output from the delay circuit 28
The output of the AND circuit 32 is supplied directly to the OR circuit 35 through a delay circuit 34 having a delay amount equal to the delay amount of .

The output of the OR circuit 35, that is, the output of the rising/falling selection circuit 25, is passed through the gate 36 to the OR circuit 2.
2. An oscillation loop cutoff signal is supplied to the gate 36 through a terminal 37. The output of the rising/falling selection circuit 25 is also supplied to the period measuring device 18 .

When the power switch is turned on in the configuration shown in FIG. 2, a pulse f _p may be generated on the output side of the rising/falling selection circuit 25 as shown in FIG. 3A, for example, and this pulse passes through the gate 36 and further Monostable multivibrator 1 through OR circuit 22
5 causes parasitic oscillations. Therefore, as shown in FIG. 3B, for a period longer than the period of the parasitic oscillation after the power switch is turned on, the terminal 37
An oscillation loop cutoff signal is applied at a low level to close the gate 36 and cut off the oscillation loop. after that,
As shown in FIG. 3C, a starting pulse is applied to terminal 21, which is triggered, for example, by the trailing edge of the oscillation loop cutoff signal. This activation pulse generates pulse oscillation in a loop including the monostable multivibrator 15 and the data under test selector 13.

Furthermore, when the selection signal at the terminal 17 is set to a high level, oscillation occurs with a pulse synchronized with the rise of the output pulse of the device under test 13. That is, the monostable multivibrator 15 is triggered by the starting pulse shown in FIG. 4A from the terminal 21, and the pulse shown in FIG. 4B is obtained at its output, which is input to the device under test 13, and its output pulse is For example, as shown in FIG. 4C. It is assumed that a control signal is applied to the terminal 24 of the data selector 23 so as to select the output pulse of the device under test 13. Therefore, the output pulse of the device under test 13 is supplied to the pulse width expansion circuit 26, and a pulse with an increased pulse width as shown in FIG. Further, it passes through the delay circuit 34 to become a delayed pulse as shown in FIG.
supplied to the gate 36 as a pulse shown in Figure F;
This triggers the monostable multivibrator 15 through the OR circuit 22. Therefore, the same process is repeated again, resulting in a pulse oscillation state. This is a pulse oscillation that is synchronized with the rise of the output pulse of the device under test 13, and the oscillation period _T1 is measured by the period measuring device 18.

Next, when the selection signal at the terminal 17 is set to a low level and a starting pulse is applied to the terminal 21 as shown in FIG. 5A, the output shown in FIG. 5B is obtained from the monostable multivibrator 15 in the same way. The output pulse of the measuring device 13 is as shown in FIG. 5C,
This output pulse is supplied to the pulse width expansion circuit 26 through the data selector 23, and its inverted output becomes as shown in FIG. 5G. This inverted output passes through the AND circuit 32 and becomes a pulse as shown in FIG. 5H. Furthermore, it is fed back to the gate 36 through the OR circuit 35 as a pulse shown in FIG. 5I. Therefore, a pulse is oscillated in synchronization with the falling edge of the device under test 13, and the oscillation period _T2 is measured by the frequency measuring device 18.

As shown in FIGS. 4 and 5, the rising edge of the output of the monostable multivibrator 15 corresponds to the measured pulse 1.
3, the delay amount of the _pulse width expansion circuit 26 is τ ₂ , each delay amount of AND circuits 31 and 32 is τ ₃ , each delay amount of delay circuits 28 and 34 is τ ₄ , OR circuit 35, the delay amount due to the gate ₃₆ and the OR circuit 22 is τ ₆ , and the output pulse width of the device under test 13 is ΔT, the period T ₁ is T ₁ = τ ₁ + τ ₂ + τ ₃ + τ ₄ +τ ₅ +τ ₆ , and the period T ₂ becomes T ₂ =τ ₁ +τ ₂ +τ ₃ +τ ₅ +τ ₄ +△T+τ ₆ . Therefore, when the difference between the period T ₂ and the period T ₁ is calculated by the calculation circuit 38, T ₂ - _{T 1} = △T, the width △T of the output pulse is obtained, and the width △
T is displayed on the display 39.

The output pulse of the monostable multivibrator 15 is selected from the data selector 23 by the control signal applied to the terminal 24, the selection signal of the terminal 17 is switched between high level and low level, and the pulse oscillation period in each case is measured. , the output pulse width of the monostable multivibrator 15 can be measured by finding the difference.

Furthermore, when the output pulse of the device under test 13 is selected from the data selector 23 with the terminal 17 set to high level, and when the monostable multivibrator 1
The delay amount τ ₁ (FIG. 4) of the rise of the device under test 13 can be measured by calculating the difference between the pulse oscillation period and the case where the output pulse No. 5 is selected.

Similarly, when the terminal 17 is set to a low level state and the output pulse of the device under test 13 is selected from the data selector 23, and the monostable multivibrator 1
By determining the pulse oscillation period for each output pulse selected and calculating the difference, the fall delay amount τ ₇ of the device under test 13 (Figure 4)
can be measured.

If the output pulse width of the device under test 13 is narrow,
In the path where this pulse is fed back to the monostable multivibrator 15, there is a risk that the pulse will not be transmitted correctly, and to prevent this from happening, a pulse width expansion circuit 26 is used. Therefore, if the output pulse width ΔT is sufficiently wide, the pulse width expansion circuit 26 can be omitted and the delay circuit 3 can be omitted accordingly.
6 can also be omitted. Since the delay amount of the delay circuit 28 cannot be made larger than the output pulse width ΔT, in order to make the pulse width sufficiently wide, for example, as shown in FIG. 6, further delay circuits 41 and 42 are added as necessary. Just set it up. The delay circuit 34 may be omitted and its delay amount may be subtracted from T ₂ −T ₁ .

"Effects of the Invention" As described above, according to the pulse width measuring device of the present invention, the pulse oscillation by the pulse synchronized with the rising edge of the output pulse and the pulse oscillation caused by the pulse synchronized with the falling edge of the output pulse are performed in the same oscillation. The pulse oscillation cycle is switched and generated in a loop, the period of each pulse oscillation is measured, and the pulse width is measured based on the difference between the two.The period measurement can be performed with high precision, making it possible to measure the pulse width with high precision. . Therefore, it is also possible to measure variations in output pulse width with high resolution and precision.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the principle of this invention, Fig. 2 is a logic circuit diagram showing an embodiment of this invention, and Fig. 3 is a block diagram showing the principle of this invention.
The figure is a time chart for explaining the stopping of parasitic oscillation in the embodiment shown in FIG. 2, and FIG. 5 is a time chart showing the waveforms of various parts of the pulse oscillation state due to the falling pulse in the embodiment of FIG. 2, FIG. 6 is a diagram showing another example of the pulse width expansion circuit 26, and FIG. 7 is a diagram showing the conventional pulse FIG. 3 is a block diagram showing a width measuring device. 13... Device under test, 15... Monostable multivibrator, 17... Rise/fall selection terminal, 18... Period measuring device, 25... Rise/fall selection circuit.

Claims (1)

[Scope of Claims] 1. An edge-triggered monostable multivibrator that supplies an output pulse to a device under test as a pulse input; an output pulse of the device under test is input;
A pulse with a leading edge synchronized with its rising edge and a pulse with a leading edge synchronized with its falling edge are selected and taken out and fed to the monostable multivibrator as a trigger pulse to form a pulse oscillation loop.Rising/falling selection A circuit, a period measuring device that measures the oscillation period in the pulse oscillation loop, and the difference between the measured values of the period of the pulse oscillation synchronized with the rising edge and the period of the pulse oscillation synchronized with the falling edge is determined as the measured pulse width. A pulse width measuring instrument comprising calculation means for calculating the pulse width.