JPH05896B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a line simulator that simulates noise that may occur on a communication line for purposes such as performance testing of communication equipment.

[Conventional technology] In recent years, with the development of digital communication technology,
Communication devices including LSIs with built-in various communication procedures have been developed, but the communication devices prototyped at the development stage are
To test and evaluate LSI, it is necessary to incorporate phenomena that can occur in actual communication channels. Particularly, actual communication paths are often contaminated with noise, and errors due to noise occur on the communication lines. Therefore, a device is known that applies a certain amount of noise to a prototype communication device and measures the error rate (occurrence rate).

[Problems to be Solved by the Invention] However, in conventional error rate measuring devices, the noise applied to the device under test is analog noise generated by an electrostatic noise generator, and its pattern is fixed to a constant value. Therefore, there was a problem in that it did not reflect the noise that could actually occur on the communication line, and it was not possible to measure error rates for various types of noise.

In order to solve this problem, the present inventors have developed a line simulator that simulates noise, signal waveform distortion, etc. that may occur on a communication line (Japanese Patent Application No. 138376/1982). This method variably sets parameters for generating noise and waveform distortion that may occur in communication lines, generates an error signal determined by the parameters from random numbers generated by a random number generating means, and generates an error signal. while
This system adds noise determined by the above parameters to the signal input from the outside and outputs the resultant signal.This allows the device under test to be immunized against various communication failures without having to install it on an actual communication line. It has become possible to test the behavior and performance of communication equipment.

In order to make the above-mentioned line simulator more practical, the present invention aims to provide an easy-to-use line simulator that allows easy operations such as setting initial values of random numbers that generate reproducible noise. do.

[Means for Solving the Problems] The present invention is a line simulator that generates noise based on random numbers on a communication line, and which generates noise based on random numbers on an initial value of the random number, the current value of the random number, and the elapsed time after startup or equivalent thereof. a display section for displaying a value, a random number initial value input means for inputting an initial random number value, a start operation means for starting an operation of adding noise to a communication line;
and an operation section including a stop operation means for stopping the operation.

The present invention also provides a parameter setting means for variably setting parameters for generating noise on a communication line, a random number generation means for generating random numbers, and a parameter setting means for setting parameters from the random numbers generated by the random number generation means. signal generating means for generating an error signal determined by the parameters set by the parameter setting means; and while the error signal is being generated, noise determined by the parameters set by the parameter setting means is added to the externally input signal. display means for displaying the initial value of the random number generated by the random number generation means, the current value of the generated random number, the elapsed time after startup, and the parameters set by the parameter setting means; The apparatus is configured to include operation means for inputting an initial random number value and for starting and stopping a noise adding operation.

[Function] In the line simulator of the present invention, the display section displays the initial value of the random number, the current value of the random number, and the elapsed time since the start of the operation, while the operation section allows input of the initial random number value, start of the noise addition operation, and Perform operations such as stopping. Therefore, the operator can know how much noise is generated within a certain period of time, and can accurately perform a performance test on the device under test. Furthermore, if the initial value of the random number is memorized, communication tests using the same noise generation can be repeated over and over again. Furthermore,
The test can also be started/stopped at any time.

In a line simulator equipped with parameter setting means for variably setting parameters for generating noise on a communication line, an error signal determined by the parameters set by the parameter setting means is generated from random numbers generated by the random number generation means. .
While this error signal is generated, noise determined by the parameters set by the parameter setting means is added to the externally input signal and output. During such a noise adding operation, the initial value of the random number, the current value of the random number, the elapsed time after startup, and the setting parameters are displayed on the display means, so that it is easy to input the initial random number value and start and stop the noise adding operation using the operating means. Can be done accurately.

[Embodiment] A line simulator 1 shown in FIG. 1 houses a circuit constituting the simulator inside a rectangular parallelepiped-shaped casing 2. The upper half of the upper surface of the casing 2 is occupied by a display screen of a display device 3 that displays as will be described later, and the lower half is configured as an operation section 4 on which various operation keys, etc. described below are arranged.
Further, on one side of the casing 2, a plurality of connectors 5 for connection to a device under test are arranged.

In use, as shown in FIG. 2, the line simulator 1 of the present invention is connected to the device under test A, and the simulator 1 performs processing to add noise to the transmission signal (communication data) to test the device under test A. send in.
By checking the operation of the device under test A, it is possible to check the behavior and performance against communication failures.

Next, the display device 3 provided in the embodiment of FIG.
consists of a liquid crystal display device, and within its display screen,
It has a 15-line display section as shown in Figure 3. Of these, the top three lines are a monitor section that displays actual measured values measured by the simulator, and consists of the following items.

Time: Displays the measured elapsed time (time elapsed since startup) in hours, minutes, and seconds (the maximum display time range is
24hours). However, the display method is not limited to this, and numbers or characters corresponding to the elapsed time may be displayed.

Line: Displays the intermittent status of the communication line.

If the communication line is connected "=========" is displayed, If disconnected “===X===” is displayed.

Bit Error Counts: Displays the number of bit errors that have occurred since measurement started.

BER: Bit Error Rate calculated using the above Bit Error Counts value
Display the value of

RND: Display the current random value.

This monitor section is a section that cannot be written to by key operations on the operation section 4, and only the title is displayed until no measurement is performed after the power is turned on.

The fourth and subsequent lines are sections that display various measurement operation conditions that can be set by key operations, and are comprised of the following items.

Line Select: Communication line standard (e.g. RS422, RS232C,
TTL).

Baud Rate: Displays the selected communication data transfer rate.
The selectable range is, for example, 1 Mbps to 300 bps.

Pulse Width: Displays the error pulse width of a single bit error. The range of pulse widths that can be selected is, for example, 1 μs to 100 ms, and can be selected at intervals of 1, 2, and 5×10 to the nth power.

Error Mode: Displays the type of bit error that occurs.
The error type refers to how the communication data is changed by adding an error, and the contents are as follows, and one of them is selected.

Thru: Do nothing.

High: Forcibly change the data to "1" by the width of the error pulse.

Low: Forcibly change the data to "0" by the width of the error pulse.

Invert: Inverts the data by the width of the error pulse.

Initial RND: Bit errors are generated by random numbers and added to communication data, but the initial value input to create the random numbers is displayed here. Since the initial value of the random number can be set, it is possible to reproduce the simulated operation.

This initial random number value, unlike the value setting items, is input as an 8-digit hexadecimal number using the 16 keys. At the end of input, it is necessary to operate the "ENTR" key, which will be described later, and the input data becomes valid only after this key input. However, if the "STRT" key described below is operated before the "ENTR" key is input, it will be assumed that the "ENTR" has been input, and the value displayed on the screen will be valid.

Err Trig Rate: This is the reciprocal of the value (number of bits) for how many bits an error is generated once, and the frequency at which a bit error is generated is displayed on this display. The range that can be selected by key operations described later is, for example, 1.49×10 ⁻⁸ to 9.76×10 ⁻⁴ , which can be set at intervals of ^1/2 .

Duty: Displays the duty ratio of communication data. The range of duty ratios that can be selected is, for example, 6.25% ~
93.75%, selectable in 3.125% intervals.

Trigger Source: Displays the measurement start trigger. This can be selected from the following:

Key: Start measurement by pressing the "STRT" key on the operation panel.

RXC P-Edge: Start measurement at the positive edge of communication data.

RXC N-Edge: Start measurement at the negative edge of communication data.

EXT P-Edge: Starts measurement at the positive edge of the external trigger signal.

EXT N-Edge: Starts measurement at the negative edge of the external trigger signal.

No matter which of the measurement start triggers above is selected, it is necessary to press the "STRT" key before the trigger signal arrives. When "Key" is selected as the trigger, measurement starts at the same time as the "STRT" key is input. Furthermore, in any case, when the "STOP" key is pressed or when a stop signal is input from the outside, the measurement stops immediately.

RXC Source: Displays the communication data synchronization signal. This can be selected from the following:

Int P-Edge: Start-stop synchronous communication synchronized with the positive edge of communication data.

Int N-Edge: Start-stop synchronous communication synchronized with the negative edge of communication data.

EXT P-Edge: Synchronous communication using the positive edge of an external synchronous clock.

EXT N-Edge: Synchronous communication using the negative edge of an external synchronization clock.

Jitter: Displays the amplitude of jitter (waveform fluctuation) added to communication data. Its value is 0%, ±3.125
%, ±6.25%.
0% is the case where no jitter is added.

BER: This is the actual error trigger rate (Err Trig Rate), error pulse width (Pulse
This item is automatically calculated and displayed by the simulator from Width) and Baud Rate, and cannot be input by key operation. The value displayed here is called the "bit error rate" and corresponds to the probability that one bit of communication data will have an error per second.

Save or Load no.: Test conditions set by key operations on the operation unit 4 are saved in the storage device of the simulator and can be retrieved and used whenever necessary. For example, up to nine types of test conditions can be stored, and the file number to be stored or retrieved is set in advance. The set file number will be displayed here.

Next, the operation unit 4 is comprised of the following keys marked with . . . in order from the left side in FIG.

``0'' to ``9'' and ``A'' to ``F'' are keys for inputting initial values of random numbers in hexadecimal numbers, etc.

“SAVE” and “LOAD” These are keys for storing and retrieving the test conditions mentioned above.

"ENTR" This is the key operated when setting the initial random number value as described above.

Four "△" keys in different directions These keys are used to move the cursor up, down, left and right on the display screen.

Two "▲" in different directions These are keys for displaying the contents of each selection item mentioned above on the screen. The contents of the selection item are "▲"
Press the key to display the next item, press the "▼" key to display the previous item.

"CUT" This is the key to cut and break the communication line. Each time you press this button, the line will be disconnected and connected alternately.

"EROR" This is a key to forcefully generate one error when necessary during measurement. The pulse width of the error that occurs is the value set in "Pulse Width" above.

“STOP” Key to stop measurement. By pressing this key, the measurement can be stopped regardless of the measurement start trigger described above.

"STRT" By pressing this key, the system enters the state of waiting for the measurement start trigger described above. Thereafter, measurement is started when the trigger selected in the "Trigger Source" is input. If "Key" is selected, measurement will start at the same time as this "STRT" key is input.

In addition to the above-mentioned operation keys, the operation section 4 is also provided with a power switch 4a and a display section 4b that lights up when an error pulse occurs.

To summarize, the line simulator 1 of the embodiment is as follows:
The initial value of the random number (Initial RND), the current value of the random number (RND), the elapsed time after the start of operation (Time), etc. are displayed on the display screen on the top of the casing, while the initial random number value is input into the operation unit 4. Operation means (cursor movement keys, 16 keys from 0 to 9 and A to F,
"ENTR" key), an operation means to start the noise addition operation ("STRT" key), and an operation means to stop the noise addition operation (the "STOP" key), it is possible to determine how much noise can be generated within a certain period of time. This makes it possible to accurately perform performance tests on the device under test. In addition, by memorizing the initial value of the random number, communication tests with the same noise generation can be repeated repeatedly.
The test can also be started/stopped at any time.

Next, the casing 2 houses a circuit that constitutes a line simulator according to the above-mentioned patent application. Its structure and operation are as follows.

First, as shown in FIG. 4, the circuit of the line simulator includes a parameter setting section 6, a control section 7, an error signal generation section 8, a clock generation section 9, and a line section 10.
Consists of.

The parameter setting section 6 is a means for setting parameters such as bit error rate for generating noise that may occur in the communication line, and is constituted by keys of the operation section 4 in this embodiment.

The control unit 7 holds the parameters input from the parameter setting unit 6, sends a display signal for causing the display device 3 to display the necessary information, and uses a random number generation circuit, which will be described later, based on the parameters set as described above. This is a part that performs operations such as selecting a generated random number and generating a bit error signal, and is equipped with the following various registers as a holding means for holding parameters set in the parameter setting section 6.
Consists of CPU. That is, the CPU has a random number initial value setting register 11, a bit error rate setting register 12, a bit error pulse width setting register 13, a bit error mode setting register 14,
It has a rising edge delay setting register 15, a falling delay setting register 16, and a line interruption register 17.

The random number initial value setting register 11 is a register for setting an initial value of a pseudo random number generation circuit 21, which will be described later. By writing an initial value to this register, the pseudo random number generation circuit 21 is directly preset. Further, by setting a certain initial value in this register, the same bit error pattern can be generated from the pseudo-random number generation circuit 21, which is effective when repeating a test.

The bit error rate setting register 12 is a register for setting the bit error rate.
Approximately 10 ^-3 to 10 ^-8 errors/bit can be set per line. Each line generates bit errors at the same bit error rate.

The bit error pulse width setting register 13 is a register that sets the pulse width when a bit error occurs, which will be described later.

The bit error mode setting register 14 specifies the type of bit error (Thru, High, Low,
This is a register for setting (Invert). If this is set to "Thru", the communication data signal will not change even when a bit error occurs, which will be described later. However, when set to "High", the input signal changes to H level "1" and is output from the line section 4 when a bit error occurs, and when set to "Low", the input signal changes to L level "1" when a bit error occurs. 0" and is output. When set to "Invert", the input signal is inverted and output when a bit error occurs.

Rise and fall delay setting registers 15 and 16
are registers that individually set the rise time delay and fall time delay that occur in the actual communication path.

If the frequency generated by the clock generating circuit 9 is set to, for example, 16 times the baud rate, a delay in units of 1/16 data bit time can be set.

The line disconnection register 17 is a register for disconnecting communication on a line-by-line basis, and can make the output from the line section 4 high impedance.

Next, the error signal generation section 8 is a section that generates an error signal for simulating phenomena that may occur in an actual communication line, and includes a pseudo random number generation circuit 21, a bit error generation circuit 22, and a bit error pulse width generation circuit. Consists of 23.

The pseudo-random number generation circuit 21 is connected between D flip-flops D ₁ to _{D 32} connected sequentially as shown in FIG.
Pseudo-random numbers are generated by interposing exclusive OR circuits E ₁ -E ₁₃ and changing the outputs X ³² -X ¹ of each flip-flop D ₃₂ -D ₁ . The pseudorandom number generation circuit itself having such a configuration is well known.

In this pseudo-random number generation circuit 21, in order to set the initial value of the random number to be generated, each D flip-flop
_D1 to _D32 have set terminals, and by inputting the output signal of the random number initial value setting register 11 to the terminals, the D flip-flops are set to the set state. That is, by writing an initial value into the random number initial value setting register 11, the register output is applied to the set terminals of the D flip-flops _D1 to _D32 , and the initial value of the pseudo random number generation circuit 21 can be preset.

The bit error generation circuit 22, as shown in FIG.
A decoder 31 decodes a bit error signal from the decoder 31, and a data selector 32 outputs only the signal to be used from among the pseudo-random numbers generated by the pseudo-random number generation circuit 21 based on the signal from the decoder 31. Outputs bit error occurrence signal when all signals are H
It consists of an AND circuit 33. As a result, when the number of random number signals selected by the data selector 32 is n, a bit error occurrence signal is output with a probability of 1/2 ⁿ .

The bit error pulse width generating circuit 23 consists of a timer 34 and an RS flip-flop 35 as shown in FIG. During operation, as shown in FIG. 8, the timer 34 is started using the output (bit error generation signal) from the bit error generation circuit 22 as a star signal, and the RS flip-flop 35 is set to generate a bit error pulse. After counting the pulse width set in the bit error pulse width setting register 13, the timer 34 resets the RS flip-flop 35. As a result, a bit error of the set pulse width is obtained. The pulse width is the set value n
It becomes n to n+1 μsec. If the next signal comes before the bit error pulse ends, the pulse width is further extended by the set value from that point onwards.

The clock generation circuit section 9 operates at a constant frequency (for example,
The frequency of the output signal from the 16MHz crystal oscillation module is divided to generate the clock signals necessary for each of the circuits mentioned above.

Next, the line section 10 is a section that processes the input signal according to the parameters given from the simulator main body 3 and outputs it, and also performs connection and disconnection of the line.

Specifically, as shown in FIG. 9, the line section 10 is
A receiver 41 that converts the level of a signal input from a transmission path, a rising detection circuit 42 that detects the rising edge of the input signal, timers 43 and 44, and a falling detection circuit 45 that detects the falling edge of the input signal.
RS flip-flop 46 and noise addition circuit 4
7 and a driver 48 that converts the level of the output signal and outputs it to the transmission path. Each detection circuit 4
2 and 45 are D flip-flops, and each timer 4
3 and 44 are respectively constituted by down counters.

During operation, when the detection circuits 42 and 45 detect the rise and fall of the input signal, the timers 43 and 44
start. Each of the timers 43 and 44 has a rise delay setting register 1 and a fall delay setting register 1 of the control unit 7, respectively.
The output is changed after a delay time determined by the signals (rise and fall delay values) sent from 5 and 16. The RS flip-flop 46 is set by a change in the output of the rise delay timer 43, and reset by a change in the output of the fall delay timer 44. As a result, a signal having a preset rise and fall delay is output as shown in FIG.

In this way, the detection circuits 42, 45 and the timer 43
and 44 and the RS flip-flop 46 are waveform conversion circuits that can delay the rise time and fall time of the signal input from the transmission path by less than 1 data bit time (until just before the next signal change). It consists of Set the setting value to n,
If the period of the clock used in this circuit is T, then
The delay time is nT to (n+1)T.

The clock signal supplied to timers 43 and 44 normally has a frequency of 16 times the baud rate, but a clock with a lower frequency can also be used to create a longer delay. in this case,
The rising delay time is until immediately before the next rising edge, and the falling delay time is until immediately before the next falling edge.

The waveform conversion circuit described above can change the duty ratio of the input signal by individually setting the rise/fall delay times. Also,
By changing each delay value, jitter (waveform fluctuation) can also be caused.

The noise output circuit 47 applies the error mode (Thru, High, Low, or Invert) specified by the output from the bit error mode setting register 14 to the signal output from the RS flip-flop 46.
When no bit error occurs (bit error pulse is L), the input signal is output as is regardless of the error mode, but when a bit error occurs (bit error pulse is low), the input signal is output as is, regardless of the error mode. When the error pulse is H), the input signal is changed and output according to the error mode.

In other words, if the error mode is Low,
While a bit error occurs, the output goes low regardless of the input; if the error mode is high, the output goes high while a bit error occurs, regardless of the input. error mode is
Similarly, in the case of Invert, the output is the inverse of the input while a bit error occurs. error mode is
In the case of Thru, even if a bit error occurs, the input signal is output as is (no noise is added).

The output signal from the above noise adding circuit 47 is
The signal is level-converted by the driver 48 and output to the transmission line, but the driver 48 is closed by the line signal from the line disconnection register 17 described above. That is, when the line disconnection register 17 outputs a line disconnection signal, the output side of the driver 48 becomes high impedance, and the transmission line can be substantially disconnected.

As described above, the illustrated embodiment is a line simulator that generates bit error pulses based on random numbers and is also capable of simulating waveform distortion and line disconnection that may occur in communication lines. In addition to displaying parameters, parameters can be set variably by operating the keys on the operation panel.When using this to perform performance tests of communication equipment, the operator can operate the keys while looking at the display screen. It has the advantage of good operability and ease of use.

Although the present invention has been described above with reference to embodiments, the present invention is not limited thereto, and the circuit, display section, and operation section constituting the line simulator may be implemented using any means as long as they have the above functions. Can be used and configured.

[Effects of the Invention] As described above, according to the present invention, parameters for generating noise that may occur in a communication line are set, and by generating noise based on random numbers, communication LSIs, etc. under test can be You can test the device without connecting it to an actual communication line. In addition, since it incorporates a display section that displays random values, etc. and an operation section for parameter settings, when using it, you can operate it while looking at the screen that displays random values, etc., improving operability and ease of use. A good effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the external appearance of an embodiment of the present invention;
The figure shows the line simulator of the present invention connected to the device under test, Figure 3 is a plan view showing an example of the display screen and the configuration of the operating section, and Figure 4 is a block diagram showing the circuit configuration of the embodiment. Figure 5 is an explanatory diagram of the pseudo random number generation circuit, Figure 6 is a configuration diagram of the bit error generation circuit, Figure 7 is a configuration diagram of the bit error pulse width generation circuit, and Figure 8 is a diagram of the bit error pulse width generation circuit. FIG. 9 is a diagram showing the configuration of the line section, and FIG. 10 is a waveform diagram showing the signal input to the waveform conversion circuit of the line section and its output signal. 1...Line simulator, 2...Casing,
3...Display device, 4...Operation unit, 5...Connector, 6...Parameter setting unit, 7...Control unit, 8
...Error signal generation section, 9...Clock generation section,
10...Line section.

Claims (1)

[Scope of Claims] 1. A line simulator that generates noise based on random numbers on a communication line, and a display unit that displays the initial value of the random number, the current value of the random number, and the elapsed time after activation or a value equivalent thereto. and an operation section including a random number initial value input means for inputting an initial random number value, a start operation means for starting an operation of adding noise to a communication line, and a stop operation means for stopping the operation. Line simulator. 2. Parameter setting means for variably setting parameters for generating noise on a communication line; Random number generation means for generating random numbers; and Parameters set by the parameter setting means from the random numbers generated by the random number generation means. signal generating means for generating a determined error signal; and while the error signal is being generated, adding noise determined by the parameter set by the parameter setting means to a signal input from the outside and outputting the resultant signal. means for displaying the initial value of the random number generated by the random number generation means, the current value of the generated random number, the elapsed time after startup, and the parameters set by the parameter setting means; inputting the initial value of the random number; , and operating means for starting and stopping a noise adding operation.