JP3773024B2 - Digital oscilloscope - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital oscilloscope, and more particularly, to an improvement in a method for sampling and storing waveform data in a digital oscilloscope.
[Prior art]
Prior art will be described. FIG. 9 is a block diagram showing a flow of signal data in the digital oscilloscope. In the oscilloscope 40, waveform data input at a constant speed is input by a thinning circuit 41, and data sampled at a set sampling speed is written into an acquisition memory (internal memory) 43 via a memory bus 42. This data is read from the acquisition memory 43 via the memory bus 42 to the PP compression circuit 44 at a predetermined timing, and a waveform is displayed on the screen via the PP compression circuit 44.
[0003]
In the oscilloscope, when the set sampling speed is sufficiently low, a free time is generated in the acquisition memory 43. Using this free time, data is read from the acquisition memory 43, compressed by the PP compression circuit 44, and displayed. This display is called a roll display and is displayed so that the current input waveform flows. When the set sampling speed is high, almost no free time is generated on the memory bus 42. Therefore, when the data acquisition is completed, the acquisition memory 43 is read and the normal waveform is read. Display.
[0004]
The oscilloscope has a function called a sequential store. In this sequential store, waveforms before and after each trigger point can be sequentially displayed based on data stored in the acquisition memory 43 in response to a trigger signal. . If there is a sequential store setting, when the trigger condition is satisfied for the input waveform, data is stored in the acquisition memory one after another. During this time, no waveform is displayed on the screen in order to reduce dead time.
[0005]
[Problems to be solved by the invention]
In the conventional oscilloscope, when the trigger condition is set in the sequential store, the trigger wait state is entered and the waveform display is not performed. For this reason, there is a problem that it is not possible to know what waveform data is currently input.
[0006]
In addition, since there is only one sampling setting, waveform data in the vicinity of the trigger point also becomes waveform data at a slow sampling point during roll display, and accurate waveform information is not displayed. .
[0007]
In addition, when there are continuous trigger points, even if the trigger point is reached, a post-trigger by the previous trigger point is displayed for the area, and a predetermined number of data in the pre-trigger area is not secured. There is also a problem that the trigger point in the input waveform is ignored.
[0008]
Furthermore, since several extra data are required outside one screen data to interpolate and display the screen waveform, if the sampling rate is slow, the time for the data necessary for interpolation is dead as it is. There is also a problem of time.
[0009]
In view of the above, the present invention improves the conventional oscilloscope and can display the trend of the current input waveform even in the trigger waiting state, and accurate waveform information even in the vicinity of the trigger point during roll display. An object of the present invention is to provide an oscilloscope capable of obtaining
[0010]
It is another object of the present invention to provide an oscilloscope that can reliably display waveform data related to a trigger point even when a trigger is continuously generated, thereby shortening a dead time.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a digital oscilloscope according to the present invention, in a first aspect, stores a data input circuit for inputting waveform data, the input waveform data, and responds to the trigger signal with the stored waveform data. A digital oscilloscope for displaying a waveform portion related to a trigger signal based on waveform data stored in the acquisition memory.
Two data input circuits for inputting common waveform data are provided. The waveform is displayed in a roll based on the data from one data input circuit, and the waveform portion related to the trigger signal is sequentially displayed by the data from the other data input circuit. In saving ,
When the waveform data stored in one block does not reach the set number of data, the waveform data stored in at least the block before the one block is copied .
[0012]
In the digital oscilloscope according to the first aspect of the present invention, both the roll display and the sequential storage with different sampling speeds are provided by the configuration including the data input circuit for the roll display and the data input circuit for the sequential storage. Therefore, it is possible to acquire the trigger point data while displaying the current waveform data. Further, the waveform data near the trigger point can employ a sampling rate suitable for sequential storage.
[0013]
A digital oscilloscope according to a second aspect of the present invention includes a data input circuit for inputting waveform data, a plurality of blocks for storing the input waveform data, and sequentially storing the stored waveform data in response to a trigger signal. A digital oscilloscope for displaying a waveform portion related to a trigger signal based on waveform data stored in the acquisition memory.
When the waveform data stored in one block does not reach the set number of data, the waveform data stored in the block before the one block is copied.
[0014]
According to the digital oscilloscope of the second aspect of the present invention, by adopting the configuration of copying the waveform data between the blocks, the waveform data necessary for each block can be ensured even if a trigger occurs continuously. There is no dead time when the waveform cannot be displayed, or the trigger disable time is shortened.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram of a digital oscilloscope according to an exemplary embodiment of the present invention. The oscilloscope 10 according to the present embodiment includes two data thinning circuits 11 and 12, a FIFO circuit 13 attached to one thinning circuit, a memory bus 14, an acquisition memory 15, two PP compression circuits 16 and 17, and an address control circuit 18. And a work RAM 19.
[0016]
The input waveform data is input to both the first data thinning circuit (1 / m thinning circuit) 11 for low-speed waveform data and the second data thinning circuit (1 / n thinning circuit) 12 for high-speed waveform data. The 1 / n thinning circuit 12 thins and samples the waveform data input at a constant speed at a set interval, sets the waveform data to an appropriate 1 / n data amount as screen display data, and obtains the obtained data. The data is input to a FIFO (First-in-First-out) buffer 13. The FIFO buffer 13 receives data from the 1 / n decimation circuit 12, and when a certain amount of data is accumulated, the FIFO buffer 13 proceeds to a write operation and sequentially outputs from the previously input data. The output of the FIFO buffer 13 is stored in each block 15b which is a memory area for high-speed waveforms of the acquisition memory 15 via the memory bus 14. The 1 / m decimation circuit 11 decimates and samples waveform data input at a constant speed at a set interval, sets the waveform data to a 1 / m data amount, and is a data area for low-speed waveforms in the acquisition memory 15. This is stored in a certain block 15a. Here, n <m. The operating speed of the 1 / m decimation circuit 11 is 100 kS (sampling) / sec at the maximum, and the operating speed of the 1 / n decimation circuit 12 is 5 MS / sec at the maximum.
[0017]
The data stored in the low-speed waveform memory block 15a of the acquisition memory 15 from the 1 / m data thinning circuit 11 continues to rotate inside the block. That is, when the storage capacity is full, the previous data is discarded sequentially, and new data is stored there. Data input from the FIFO buffer 13 and stored in each block 15b of the high-speed waveform memory area of the acquisition memory 15 continues to rotate inside the block 15b until the trigger condition is satisfied. When the trigger condition is satisfied, after storing a predetermined number of data in the post-trigger area, the process proceeds to the memory block 15b for the next high-speed waveform, and the data continues to rotate in that block until the next trigger is present.
[0018]
In order to display the roll waveform, the first PP compression circuit 16 sequentially reads the latest waveform data from the low-speed waveform memory block 15b of the acquisition memory 15 and compresses it by PP (Peak-to-Peak). Display on the screen. The second PP compression circuit 17 reads the waveform data after the trigger condition is satisfied and each block 15b in the high-speed waveform memory area of the acquisition memory 15 has a predetermined amount of data, and compresses the waveform data to perform screen compression. Prepare for display.
[0019]
On the screen 20, a low-speed waveform is continuously displayed in the upper part, and waveforms before and after the trigger point when the trigger condition is satisfied (the waveform in the pre-trigger area and the posttrie area) are displayed in a predetermined condition on the lower part. Is done. In the present embodiment example, a configuration in which one oscilloscope is provided with the two data thinning circuits 11 and 12 and the two PP compression circuits 16 and 17 has a waveform when the trigger condition existing in the conventional oscilloscope is set. Excludes disadvantages that cannot be seen.
[0020]
FIG. 2 is a timing chart showing an example of the waveform data in the above embodiment with time. The memory bus 14 has a sufficient bandwidth that enables high-speed transfer. Writing of low-speed sampling data, writing of high-speed sampling data, PP compression operation for roll display, and PP for high-speed sampling display Data transfer necessary for the four operations of the compression operation is executed in parallel.
[0021]
In low-speed sampling, sampling is executed once every 10 μs, and in high-speed sampling, sampling is executed once every 200 ns. The result of the low-speed sampling is written into the acquisition memory 15 via the memory bus 14 at a predetermined timing, and the result of the high-speed sampling is once stored in the FIFO buffer 13 and when a predetermined number of samplings are performed, Data is written to the acquisition memory via the memory bus 14 at high speed. The memory bus 15 is further used by two PP compression circuits 16 and 17, and each PP compression circuit 16 and 17 reads data from the acquisition memory 15 and processes it in the interval of high-speed sampling.
[0022]
FIG. 3 schematically shows accumulation of waveform data in the acquisition memory 15 obtained as a result of sampling by the data thinning circuits 11 and 12. The acquisition memory 15 is divided into a plurality of blocks 15a and 15b1 to 15bN each storing 100k data points, and keeps rotating while storing the low-speed sampling data in the first block 15a. The number of rounds of data is stored on the hardware. In each of the blocks 15b1 to 15bN after the second block, waveform data obtained by high-speed side sampling is stored as page data. The size of each block 15a, 15b is set according to the waveform data to be measured.
[0023]
In the example shown in the figure, the trigger is applied at the zero cross point where the waveform data shifts from positive to negative. When a trigger is generated, the address control circuit 18 triggers on every cycle of the low-speed waveform data for each trigger. The address in the memory block 15a on the low speed side of the trigger, the end address in the memory block 15b on the high speed side, and the number of fetched data in the memory block 15b on the high speed side are written in the work RAM 19. For example, when the operator selects one trigger point in the low-speed waveform on the screen, the pre-trigger area data and the post-trigger area data including a predetermined number of data corresponding to the trigger point are extracted from the acquisition memory 15b. . The second PP compression circuit 17 reads and compresses this data in advance and displays it on the screen according to the request.
[0024]
Here, as shown in FIG. 3, when the next trigger occurs before the acquisition of the waveform data in the post-trigger area that is required to be displayed by the previous trigger is completed, the pre-trigger area in the next trigger is generated. There is a situation where the waveform data is insufficient. In this case, this is detected by the number of acquisitions stored in the work RAM 19, and the shortage is copied between the blocks 15b. Predetermined hardware is provided for this copy. The transfer source address and the transfer destination address are set by software. When a transfer having an address whose transfer source crosses a block boundary occurs, copying is performed in a plurality of times. The block size is determined in consideration of the number of data in the pre-trigger area and the post-trigger area, and the transfer destination address does not cross the block boundary.
[0025]
According to the oscilloscope of this embodiment example, long-time waveform acquisition and high-speed waveform acquisition can be executed by one oscilloscope, and the current input waveform is sequentially displayed by low-speed sampling even in the state of waiting for a trigger. I can do it. When a trigger occurs when performing low-speed sampling, if a trigger point on the low-speed waveform is specified, the required high-speed sampling waveform data is located at any position in the low-speed sampling waveform data depending on the data stored in the work RAM 19 The high-speed waveform can be displayed on the screen 20 based on the data. In this case, since the whole image is obtained by slow sampling and the portion to be analyzed is sampled at high speed, the acquisition memory 19 can be used effectively.
[0026]
In the present embodiment, the case where the low-speed sampling / high-speed sampling is executed by the two data thinning circuits 11 and 12 has been described. However, if it is within the transfer capability of the memory bus, two triggers are input to one input waveform data. It is also possible to set the conditions and cause the thinning circuits 11 and 12 to sample simultaneously.
[0027]
FIG. 4 shows the configuration of an oscilloscope according to the second embodiment of the present invention. The oscilloscope 30 includes a trigger circuit 31 that generates a trigger signal when a trigger condition is established based on waveform data, a FIFO buffer 32 that has a first-in first-out function and receives waveform data, and data from the FIFO buffer 32 via a memory bus 33. An acquisition memory 34 that receives, stores, and stores the trigger signal based on the trigger signal, a control circuit 35 that specifies the address of the acquisition memory 34, and data related to the data stored in response to the trigger signal is provided for each trigger signal. And a work RAM 36 which is stored every time.
[0028]
The acquisition memory 34 is divided into blocks 34a1-34aN, each of which can store 100k data points. The data stored in the work RAM 36 includes the end address of the post-trigger area for each trigger and the number of valid data stored in the acquisition memory for each trigger point.
[0029]
FIG. 5 shows processing in the oscilloscope of this embodiment. The oscilloscope starts operation when there is a sequential store instruction, and captures data into the acquisition memory 34 via the FIFO buffer 32 and monitors the trigger circuit 31 for establishment of the trigger condition. When the trigger condition is satisfied, the control circuit 35 receives a signal to that effect via the FIFO buffer 32, stores the sequential data at that time in the respective blocks 34a1 to 34aN of the acquisition memory 34, and data related thereto. Is stored in the work RAM 36.
[0030]
In data acquisition, when there is a first trigger, as shown in FIG. 6, data for the post-trigger area from the display start position of the first block 34a is saved, and predetermined data corresponding to the work RAM is stored. Next, the write address is set to the head of the next block 34a2, and the data from the FIFO buffer 32 is sequentially written. At this time, if the trigger condition is satisfied even in the pre-trigger area, the data in the post-trigger area is saved from that point. When a predetermined amount of data is obtained, the process proceeds to the next block. When data is obtained for the set number of triggers, the data fetching process is terminated (step S1).
[0031]
In FIG. 5, when the data acquisition is completed, the oscilloscope shifts to processing for waveform display. Data corresponding to the first trigger is read from the work RAM 36 (step S2), and the record length of the data stored in the first block 34a1 of the acquisition memory 34 is checked (step S3). Since the trigger is disabled for the first trigger and display by the trigger is not performed, the process proceeds to step S5 to determine whether or not the block of the set number of times has been examined, and if it is less than the set number of times. If so, the process returns to step S2 and proceeds to the processing of the next block.
[0032]
The data for the next trigger point stored in the work RAM 36 is examined, and if a predetermined record length is recorded, the process proceeds to the next block. On the other hand, as shown in FIG. 6, since a trigger has occurred in the middle of the pre-trigger area, if the number of data in the pre-trigger area is insufficient in the block 34a2, the waveform data is insufficient due to the short record length. The effect is detected. Since this deficient data is stored as data in the post-trigger area in the previous block 34a1, it is copied as data in the pre-trigger area of the block 34a2 (step S4). In this way, waveform data for all trigger points except for the first block 34a1 is obtained. When all the waveform data is available, the process is terminated, and the waveform is displayed after waiting for a waveform display command.
[0033]
FIG. 7 illustrates a typical waveform displayed in response to a trigger signal on the oscilloscope. Fig. (A) shows the case where the front and rear regions of the same size are displayed with the trigger point as the center, and Fig. (B) shows the case where the trigger point is displayed at a position 10% from the front of the entire display region. FIG. 8C shows a case where the trigger point is displayed at a position 10% from the back of the entire display area. In the conventional oscilloscope, in the cases of (a) and (c), the pretrigger area cannot be displayed because the pretrigger area overlaps the posttrie at the previous trigger point. FIG. 8 shows the conventional display in the case of FIG. 7A, and shows that the waveform data cannot be displayed as shown by the wavy line. However, according to this embodiment, the wavy line portion can be displayed by copying data between blocks.
[0034]
Although the present invention has been described based on the preferred embodiment, the digital oscilloscope of the present invention is not limited to the configuration of the above embodiment, and various modifications can be made from the configuration of the above embodiment. Further, modifications and changes are also included in the scope of the present invention.
[0035]
【The invention's effect】
As described above, according to the digital oscilloscope of the first aspect of the present invention, there is an advantage that waveform data can be continuously displayed by one data input circuit even when sequential storage is performed. Further, according to the digital oscilloscope of the second aspect of the present invention, when data in each memo block of the acquisition memory is insufficient in sequential storage, the insufficient data is copied from the block before the block. Therefore, since the block data is used, it is possible to display a necessary waveform even if triggers are generated continuously.
[Brief description of the drawings]
FIG. 1 is a block diagram of an oscilloscope according to an embodiment of the present invention.
FIG. 2 is a timing chart of data transfer in the oscilloscope of FIG.
FIG. 3 is a schematic block diagram showing how data is stored in a sequential store.
FIG. 4 is a block diagram of a digital oscilloscope according to a second embodiment of the present invention.
FIG. 5 is a block diagram showing processing of the digital oscilloscope of FIG. 4;
FIG. 6 is a block diagram of an acquisition memory showing a state of copying between blocks.
FIG. 7 is a waveform diagram showing various cases of pre-trigger area and posttrie at the trigger point for displaying the area.
FIG. 8 is a waveform diagram in sequential display in the case of FIG.
FIG. 9 is a block diagram of a conventional digital oscilloscope.
10, 30: Digital oscilloscope 11, 12: Data thinning circuit 13, 32: FIFO buffer 14, 33: Memory bus 15, 34: Acquisition memory 16, 17: PP compression circuit 18, 35: Control circuit 19, 36: Work RAM
31: Trigger circuit

Claims (2)

A data input circuit for inputting waveform data, and an acquisition memory having a plurality of blocks for storing the input waveform data and sequentially storing the stored waveform data in response to a trigger signal, are stored in the acquisition memory. In a digital oscilloscope that displays the waveform portion related to the trigger signal based on the waveform data,
Two data input circuits for inputting common waveform data are provided. The waveform is displayed in roll form using the data from one data input circuit, and the waveform part related to the trigger signal is sequentially displayed using the data from the other data input circuit. In saving ,
A digital oscilloscope characterized in that, when the waveform data stored in one block does not reach the set number of data, the waveform data stored in at least the previous block is copied . A data input circuit for inputting waveform data, and an acquisition memory having a plurality of blocks for storing the input waveform data and sequentially storing the stored waveform data in response to a trigger signal, are stored in the acquisition memory. In a digital oscilloscope that displays the waveform portion related to the trigger signal based on the waveform data,
A digital oscilloscope that copies waveform data stored in a block before the one block when the waveform data stored in one block does not reach a set number of data.

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