JPH0810235B2 - Waveform display device - Google Patents

Description

The present invention relates to a waveform display device, and more particularly to a waveform display device capable of repeatedly overwriting and displaying data corresponding to an input signal in a memory without omission.

[Prior Art] In a waveform display device such as a digital storage oscilloscope, an analog input signal is converted (digitized) into digital waveform data and sequentially stored in a memory, and the input signal is converted based on the waveform data stored in the memory. The displayed waveform is displayed on a display device such as a CRT (cathode ray tube). Waveform data representing an input signal is stored in a memory with reference to a trigger event Tr that occurs when the input signal crosses a predetermined trigger level with a predetermined polarity. The state of this operation is shown in FIG. The memory write operation W is started in response to the write start signal WS, and the write operation is stopped in response to the trigger event Tr. Immediately thereafter, the memory starts the read operation R, and the waveform data is sequentially read and displayed. After the read operation for a predetermined period, the write operation starts again in response to the write start signal WS. When the above operation is repeated and the input signal is a repetitive signal, a stable waveform can be displayed based on the trigger event.

Typical digitizing (analog-to-digital conversion) techniques for input signals include equivalent time sampling techniques such as real time techniques and sequential sampling techniques. In the real-time technique, the input signal is digitized at a high density in sequence according to the constrained clock signal.
In order to correctly reproduce the input signal, it is necessary to perform digitization using a clock signal having a frequency twice or more the frequency of the input signal according to the so-called sampling theorem, but a single-shot signal can also be digitized. On the other hand, in the equivalent time sampling technique, a clock signal having a frequency lower than that of the repetitive input signal is used to sequentially sample the waveform data little by little for each input signal of one cycle or more, and the sampling positions are sequentially or Randomly shift,
The waveform data of the repetitive input signal is reproduced by reconstructing all the obtained waveform data later. This equivalent time sampling technique can digitize extremely high frequency repetitive input signals with a relatively low frequency clock signal, but cannot accurately digitize single-shot or non-repetitive signals.

[Problems to be Solved by the Invention] As described with reference to FIG. 3, since the write operation W and the read operation R of the memory are alternately executed, the digitizing of the input signal is performed during the read operation R. And writing is not possible. Therefore, since it is impossible to capture the state of the input signal during the read period, when it is desired to capture an abnormal waveform that occurs extremely rarely (for example, about once every 1 million pulses), the capture probability becomes extremely low. Occurs. For this reason, it is possible to
While one memory has been made to execute the write operation to the other memory during the read operation to eliminate the omission of information capture, there is a drawback that the configuration and control become complicated.

Further, when the above-mentioned equivalent time sampling technique is used, since the clock frequency of the digitizer is relatively low, for example, 100 KHz, it is possible to insert a read operation during a write operation and execute them simultaneously equivalently. there were.
However, with the equivalent time sampling technique, it is difficult to capture an abnormal waveform that occurs extremely rarely, because it is not continuously and densely digitized with time. A real-time technique of sequentially digitizing at high density is preferable to capture such rare abnormal waveforms, but since high-speed digitizing by a high-frequency clock signal is required, simultaneous writing and reading are required. It was difficult to execute and eliminate the omission of information acquisition.

Therefore, an object of the present invention is to provide a waveform display device using a real-time digitizing technique capable of capturing and displaying the waveform data of an input signal for a desired period with a simple structure without any information leakage. That is.

[Means for Solving the Problems] According to the waveform display device of the present invention, the analog-to-digital conversion means (digitizer) causes the above-mentioned input signal for a predetermined period on the basis of the trigger event repeatedly generated according to the input signal. Real-time waveform data representing the values of a plurality of points are sequentially generated. The waveform data from the analog / digital converting means is repeatedly overwritten in the bit map memory for each trigger event. Furthermore, even while waveform data is being written to the bit map memory,
Based on the waveform data from the bit map memory,
The display means displays a waveform representing the input signal.

[Operation] According to the present invention, the real-time waveform data is sequentially overwritten in the bit map memory without being interrupted, and the display based on the waveform data is performed even during this writing period. Can be continued for an arbitrary predetermined period, and an abnormal signal that occurs extremely rarely can be reliably captured.

[Embodiment] FIG. 1 is a block diagram showing the configuration of a preferred embodiment according to the present invention. An input signal input to the input terminal 10 is adjusted to an analog signal within a predetermined range by a vertical amplification unit 12 including an attenuator and a vertical amplifier, and supplied to a digitizer (analog / digital conversion means) 14. Digitizer 14
Generates a real-time waveform data Y representing a plurality of values of the input signal by sequentially digitizing (analog-to-digital conversion) the analog input signal according to the clock signal supplied from the time base and control circuit 16. To do. This waveform data is sequentially written in the bit map memory 18 according to the time base and the X address signal from the control circuit 16. A trigger circuit is also included in the vertical amplification unit 12, and a trigger signal (trigger event) is generated when an input signal crosses a predetermined trigger level with a predetermined polarity. Each time this trigger event occurs, the time base and control circuit 16 resets the X address signal of the bit map memory 18 and repeats the write operation.
Overwrite the waveform data of the input signal. As described above, since the repetitive waveform data is written based on the trigger event, if the input signal is an accurate repetitive signal, constant waveform data is always stored in the bit map memory 18. The waveform data stored in the bit map memory 18 is sent to the display control circuit 20. Display control circuit 20
Receives the horizontal axis scanning signal (X) from the time base and control circuit 16, receives the waveform data from the bit map memory 18 as a vertical signal (Y), and represents the input signal based on these signals. Waveform raster scan type CRT
Such a display device 22 is displayed on the screen of the display device 22.

FIG. 2 is a diagram for explaining the operation of the bit map memory 18 of FIG. The memory 18 starts the write operation W in response to the write start signal WS from the time base and the control circuit 16, the X address is reset every time the trigger event Tr occurs, and the waveform data is overwritten. As described above, during the period in which the contents stored in the bit map memory 18 are not erased and the overwriting is repeated, the input signal is always captured in accordance with the clock signal, and the information due to the interruption as in the conventional case is stored. No trap omission occurs. After the write operation is repeated for the predetermined period set by the operator, the write operation is stopped by the first trigger event and the waveform data accumulated in the bit map memory 18 is displayed in the display memory in the display control circuit 20. Transfer (period T). afterwards,
All the contents of the bit map memory 18 are erased (period D). Immediately thereafter, the write operation W is started again in response to the write start signal WS, and the same operation is repeated thereafter. On the other hand, the waveform data stored in the display memory (not shown) in the display control circuit 20 is repeatedly read and displayed on the display device 22. As a result, even during the writing operation to the bit map memory 18, the accumulated waveform of the input signal can be displayed on the display device 22 at the same time. In this way, start writing WS
By setting the period from to the waveform data transfer operation T to be sufficiently long, it is possible to remarkably increase the possibility of capturing an abnormal waveform having a very low occurrence frequency. If the input signal is a repetitive signal, the abnormal waveform is displayed clearly different from the normal waveform and can be confirmed at a glance. In the above operation, the interruption of the write operation is performed during the transfer period T of the waveform data.
And the erase period D of the bit map memory 18,
This interruption period is extremely short as compared with the duration of the write operation, so that there is practically no problem. Further, in FIG. 2, the waveform data transfer period T and the erasing period D are continuous, but it is not necessary to perform these processes continuously,
As a matter of course, it can be executed at a desired time as needed. Furthermore, if a dual port memory capable of simultaneous writing and reading operations is used as the bit map memory 18, the transfer period T can be eliminated. Such a high-speed dual-port memory is disclosed in, for example, Japanese Patent Laid-Open No. 1-100790 “Multi-port memory”.
Is disclosed in. Note that in the above description, writing is immediately stopped in response to a trigger event for the sake of convenience. However, by driving the delay counter in response to the trigger event, the write operation is stopped after an arbitrary period has elapsed from the trigger event. Then, it goes without saying that functions such as so-called pre-trigger and post-trigger for arbitrarily controlling the position of the trigger point on the displayed waveform can be added. Further, as the digitizer 14, for example, a high-speed parallel comparison type analog-digital converter is used, and the output of the thermometer code is supplied to the exclusive OR gate, whereby the vertical direction of the bit map memory 18 is increased. The data Y can be obtained easily and at high speed. Further, in FIG. 2, the waveform data is written in the memory on the basis of the trigger, but it may be operated in the free-run mode in which the waveform data is written in the memory regardless of the trigger. Further, the present invention can be applied not only in the case of repetitive signals but also in the case of non-repetitive signals or single-shot signals so as to accumulate repetitive waveform data.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the embodiments described herein, and various modifications and changes can be made as necessary without departing from the gist of the present invention. It will be apparent to those skilled in the art that this is possible.

[Effects of the Invention] According to the present invention, real-time waveform data is sequentially overwritten in the bit map memory without interruption, and display is performed based on the waveform data from the bit map memory even during this writing period. As a result, the write operation can be continued for an arbitrary predetermined period and all the waveform information can be accumulated according to the period even with a simple configuration, so that even an abnormal signal that occurs extremely rarely can be reliably captured. It will be possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a waveform display device according to the present invention, FIG. 2 is a diagram for explaining the operation of the bit map memory of FIG. 1, and FIG. 3 is a conventional waveform. It is a figure for explaining operation of a memory in a display. 14: Analog-to-digital conversion means (digitizer) 18: Bit map memory 20 and 22: Display means

Claims (1)

[Claims] 1. An analog-to-digital conversion means for sequentially generating real-time waveform data representing the values of a plurality of points of the input signal in a predetermined period with reference to a trigger event repeatedly generated in response to the input signal. A bit map memory for receiving waveform data from the analog / digital conversion means, and repeatedly and continuously overwriting waveform data for each cycle of the input signal for each trigger event; A waveform display device comprising: display means for displaying a waveform representing the input signal in accordance with the waveform data from the bit map memory even while the waveform data is being written in the memory. .