JPH0543271B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveform acquisition device, such as a digital storage oscilloscope, that allows the invention of a trigger to be visually observed.

[Prior art]

Observing events at frequencies as low as 1 Hz is difficult with conventional (non-storage) oscilloscopes. This is because it is difficult to sweep the trace across the oscilloscope screen slowly enough and maintain an afterimage of the drawn waveform display. This problem is solved with a digital oscilloscope (DSO).

In a DSO, a signal representing an event is sampled at a predetermined rate, the sampled values are stored in memory in a time-related manner, and the contents of this memory drive the oscilloscope display after signal acquisition. Ru.

The contents of a digital oscilloscope's memory are waveform records that virtually make up the display. That is, this waveform record or a portion thereof can be used for visual display. However, it is not always necessary to use the waveform record for visual display. In scan mode of DSO operation, updating of the waveform record is performed as follows. That is, each time a new sample is taken, that sample is added to the waveform record without affecting the information already stored. When visual display is performed using this waveform record, each time a new sample is added, the displayed waveform is updated by extending it to the right by one sample point. When the DSO operates in roll mode, when a new sample is stored, the oldest information remaining in memory is erased from the waveform record. When this waveform record is used for visual display, each time a new sample is taken, the displayed waveform is shifted to the left by one sample point so that the most recent sample always appears at the same horizontal position on the screen.

Scan mode allows the DSO operator to contrast newly acquired waveform information against a background of previously acquired waveform information, while roll operation mode allows the DSO operator to continue acquiring data indefinitely, regardless of waveform memory capacity. You can continue to apply.

Additionally, DSO allows you to observe events that occur before and after a trigger event. Once a certain trigger event is determined, the waveform record generated by the DSO must include the time point at which the trigger event occurred, and the signal acquisition termination operation is initiated based on the occurrence of the trigger event.

In most DSOs, the signal acquisition device begins operation in a pretrigger fill state, enters a trigger ready state, and after receiving a trigger moves to a post trigger fill state. When the waveform record is completed by receiving a sufficient number of samples in the post-trigger sufficiency state, signal acquisition ends.

[Problem that the invention seeks to solve]

However, conventional DSOs lack a means to notify the operator that a trigger event has occurred.

An object of the present invention is to provide a waveform acquisition device that allows an operator to easily perceive the occurrence of a trigger event when observing an input signal that changes very slowly.

[Means for solving problems]

The waveform acquisition device of the present invention includes an acquisition circuit 4 that sequentially converts an input signal into waveform data, a waveform memory 8 that stores the waveform data, and a waveform memory 8 that stores data before a trigger event in accordance with pre-trigger settings. and control means 6 for controlling the waveform memory so that after storing a predetermined number of pre-trigger waveform data, post-trigger waveform data after the trigger event is stored in the remaining storage area of the waveform memory.

According to this waveform capture device, the control means 6
The trigger controller sequentially stores the predetermined number of print trigger waveform data in the waveform memory, and then sequentially erases the oldest pre-trigger waveform data in the waveform memory each time new waveform data is stored. The post-trigger waveform data continues until the trigger event, and after the trigger event, the post-trigger waveform data is controlled to be sequentially stored in the remaining storage area of the waveform memory.

〔Example〕

FIG. 1 embodies the waveform acquisition device of the present invention.
FIG. 2 is a simplified block diagram of DSO 15. DSO15 is
Signal acquisition circuit 4 of test point (not shown)
It has a probe 2 for guiding. In the acquisition mode of the DSO 15, the acquisition circuit 4 digitizes the test point signal under the control of a controller 6 including a microprocessor and inputs the digital signal into the waveform memory 8 to form a waveform record. . Samples are taken periodically, and the address of the memory location into which the sample value is written corresponds to the time the sample was taken. The effective sampling rate is determined by the sampling rate controller 7. Control unit 7 is 50ns/sample (20MHz) to 50
Sampling speed can be set in 1, 2, or 5 series up to mg/sample (20Hz). By supplying a sampling control signal from the outside via the signal line 11, an arbitrarily long sampling period can be obtained. In the illustrated DSO, the invention is implemented only at low sampling rates, eg, below 1 kHz (1 ms/sample).

In the display mode, sample values stored in the waveform memory 8 are read out and converted into analog signals by a digital to analog converter (DAC) 9. Based on this analog signal, the vertical deflection amplifier of the CRT 12 of 10.24 horizontal divisions (div) is driven.

The time-related address signal for reading data from the waveform memory 8 is converted into an analog signal by the DAC 13, and based on this signal, the CRT
Twelve horizontal deflection amplifiers 14 are driven.

Waveform memory 8 has 4096 individual address locations, so when all address locations are filled, waveform memory 8 becomes a waveform record consisting of 4096 digital words. DAC13 converts a 10-bit digital word, so the horizontal deflection signal is 1024
Can take on several different values. Therefore, CRT1
Up to 1024 sample points of 2 can be displayed.

The number of sample points displayed on the CRT is
It depends on the TIME/DIV control section 16 and the sampling rate. The TIME/DIV control unit 16, like the sampling rate control unit 7, has a predetermined number of settings, for example, 1, 2, and 5 series from 50 ns/div to 5 s/div. As an example, if the waveform record is approximately
The sampling rate is set to 5ms/sample to correspond to the acquisition period of 20s (5ms x 4096 samples), and TIME/DIV is set in the display mode.
is set to 5ms/div, only 10 sample points corresponding to a display period of 50ms will be displayed.
It will be displayed on a 10.24 div screen.
Also, if TIME/DIV is set to 2ms/div, the display period will be 20ms, and 4 of the waveform records will be displayed.
Only these sample values are used for waveform display.
If TIME/DIV is set to 0.5s/div, the display period will be 5s and 1024 sample values will be used for display.

TIME/DIV control unit 1 so that the display width corresponds to a display period shorter than the waveform record acquisition period.
When set to 6, the portion of the waveform record to be displayed is selected by the active cursor control section 18. The active cursor is defined as follows. That is, when the active cursor is moved horizontally, the display period moves relative to the capture period so that the cursor remains on the screen.

DSO is an event of interest (trigger event)
It is often used to observe waveforms that include events that occur before the trigger event (pre-trigger event) and events that occur after the trigger event (post-trigger event). The trigger event itself can be defined by the magnitude of a signal that crosses a band (range) of predetermined values in a predetermined direction (+ or -). Once the trigger event is determined, the operator determines how much of the waveform record to allocate to the pre-trigger portion. For example, the operator may inhibit the start of the signal acquisition end operation until 25% of the waveform memory (i.e., 1024 samples) is filled with samples, and when 1024 samples are received, the controller 6 may close the signal line 17. It can be determined that a trigger enable signal is sent to the acquisition circuit 4 via the DSO 15 to enter a trigger standby state. D.S.O.
When the acquisition circuit 4 detects a valid trigger event while the controller 15 is in the trigger standby state, a trigger signal is sent to the controller 6 via the signal line 19, and the controller 6 enters the post-trigger sufficiency state.

The DSO 15 of FIG. 1 may operate in a roll mode or a scan mode during the acquisition of signals representative of low frequency varying events.

As shown in Figure 2a, the events of interest are signal changes 32, 34, 36 and signal changes 38,
When attempting to observe a waveform containing a sequence of events other than 40, 42, the DSO operator must:
The DSO can be controlled to generate a trigger signal when the signal crosses band 44 upward (+) and a trigger enable signal to occur when 1/4 of the waveform record is filled. This ensures that the final waveform record contains not only trigger event information, but also information about the desired events before and after it.

The waveform memory 8 is updated in scan mode until the trigger enable signal is generated after signal acquisition is started. 2b, 2c, and 2d show virtual display waveforms at times t ₁ , t ₂ , and t ₃ after the start of signal acquisition (t=0), respectively. As can be seen from these figures, at a time t earlier than T/4, each new sample is added to the waveform memory 8 without affecting the information already stored in the waveform memory 8. The dashed line in FIG. 2d shows the evolution of the virtual display if the waveform memory were to continue to be updated in scan mode after time _t3 . When the signal acquisition reaches the trigger enable point, the controller switches from scan mode to roll mode, and the 2e, 2f
As shown, each time a new sample is stored, the oldest sample in waveform memory 8 is erased. When a trigger event occurs (Figure 2g),
The controller 6 returns to scan mode and remains there until signal acquisition is complete, ie, until waveform memory 8 is filled (see Figure 2h).

Therefore, if this waveform record is used for visual display, a change from scan mode to roll mode will become a visual indication to notify the operator that the trigger enable point has been reached, and a change from roll mode back to scan mode will be a trigger. This serves as a visual display to notify you of the occurrence of an event. Even if the waveform record is not used for visual display, the change from scan mode to roll mode and from roll mode to scan mode can be used to change from pre-trigger sufficiency state to trigger standby state and then back from trigger standby state. A change in state of the DSO to a post-trigger sufficiency state can be indicated in a perceptible manner.

To facilitate roll mode operation, the waveform record is configured to start at any location in the waveform memory 8 and return to the initial location when the last location is filled. For example, in the case of Figure 2, the time point
If signal acquisition begins at a certain time (t=0) such that t ₄ , t ₅ , and t ₆ correspond to memory locations 3000, 3050, and 3100, respectively, then the time t ₄ +T/4, t ₅ +T /4,
t ₆ +T/4 are memory locations 4024, 4074, and 0028, respectively.
(4124−4096), and time t ₆ +T is the memory location
Corresponds to 3099.

The present invention is not limited to the specific embodiments described above, and various modifications and changes can be made. For example, the waveform memory and display need not be integrated into the same device; the display may be part of a mainframe oscilloscope, and the acquisition circuitry, waveform memory, and controls may be part of a plug-in digitizer. . It is not necessary that the controller be microprocessor-based. For example, the controller may alternatively be configured with a state machine based on a programmable logic array.

〔Effect of the invention〕

According to the waveform capture device of the present invention, for an input signal that changes slowly, in the pretrigger state before a trigger event, after predetermined pretrigger waveform data is sequentially stored in the waveform memory, each time new waveform data is stored. Since it operates in a so-called roll mode in which the oldest pretrigger waveform data is sequentially erased, the operator can clearly perceive the pretrigger state from the display state. Furthermore, after the trigger event occurs, the operation changes to sequentially storing the post-trigger waveform data in the waveform memory, so it is easy to visually perceive the post-trigger state at the time the trigger event occurs and thereafter.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a digital storage oscilloscope using the waveform acquisition device of the present invention.
FIG. 2 is a waveform diagram for explaining the operation of the oscilloscope shown in FIG. In the figure, 4 is a capture circuit, 6 is a control means, 8 is a waveform memory, 9 and 13 are DACs, and 12 is a CRT.

Claims (1)

[Claims] 1. An acquisition circuit that sequentially converts an input signal into waveform data, a waveform memory that stores the waveform data,
After storing a predetermined number of pre-trigger waveform data before the trigger event in the waveform memory according to the pre-trigger settings, the waveform is stored in the remaining storage area of the waveform memory to store post-trigger waveform data after the trigger event. and a control means for controlling a memory, wherein the control means sequentially stores the predetermined number of the pre-trigger waveform data in the waveform memory, and then stores the pre-trigger waveform data in the waveform memory each time new waveform data is stored. The operation of sequentially erasing the oldest pre-trigger waveform data in the waveform memory is continued until the trigger event, and after the trigger event, the post-trigger waveform data is controlled to be sequentially stored in the remaining storage area of the waveform memory. A waveform capture device characterized by: