CN1691020A - Method for fast generation of pseudo-random code as driving source for simulation - Google Patents

Abstract

The invention discloses a method for quickly generating a pseudo-random code excitation source for simulation. The method comprises: determining the fixed repetition period sequence of the pseudo-random sequence and the model parameters of the pseudo-random code excitation source; using the model parameters to describe the pseudo-random code excitation source; The waveform of each pseudo-random code excitation source in the random sequence generates a description file; when the simulation is performed, the description file is directly called by the simulation program, and the actual model parameter values are used to replace the corresponding model parameters in the description file. The pseudo-random code excites the source signal; and the excitation system is simulated by using the generated pseudo-random code to excite the source signal.

Description

A method for quickly generating pseudo-random code excitation source for simulation

technical field

The invention relates to simulation technology in the field of electronics and communication, in particular to a method for quickly generating pseudo-random code excitation sources for simulation.

Background technique

In communication products, as the operating frequency of the system becomes higher and the system becomes more and more complex, the demand for signal integrity analysis through board-level simulation and system-level simulation is becoming more and more urgent. A printed circuit board does not go through The design method of using board-level simulation analysis to cast boards and then finding problems during debugging can no longer meet the requirements of market development.

In order to simulate the system signal quality when the system is open to business, an excitation source signal is generally used to stimulate the system to perform bit error simulation without services. The excitation source signal is the pseudo-random code excitation source. The pseudo-random code excitation source has the following characteristics:

(1) The pseudo-random sequence is a definite sequence generated by the shift register, which repeats stably with a certain period.

(2) Pseudo-random sequences have some random characteristics of true random sequences.

(3) The numbers of the two elements "0" and "1" in the sequence are almost equal (the difference is only 1), each accounting for about 1/2 in the sequence.

In the scheme of establishing the simulation model of the pseudo-random code excitation source, the existing implementation schemes all adopt the shift register method to establish the simulation model of the pseudo-random code excitation source. The method is as follows:

Method 1. Using HSPICE (a high-speed simulation software for integrated circuits) to realize the shift register, and processing it with non-HSPICE software to establish a pseudo-random code excitation source simulation model. Its implementation process is shown in Figure 1:

Build the shift register simulation circuit by HSPICE; run the HSPICE simulation output shift sequence; use non-HSPICE software to process the shift sequence; run to generate the simulation model accepted by HSPICE; HSPICE calls the model for simulation.

This method has the following disadvantages:

1. The simulation model of the pseudo-random code excitation source is generated because it needs multi-step processing and multiple software synthesis, so its speed is relatively slow.

2. The pseudo-random code excitation source simulation model cannot be generated directly in HSPICE, but the result generated by the HSPICE shift register must be processed by non-HSPICE software before it can be used, so the cost is relatively high.

3. Generating and calling the simulation model cannot be performed at the same time.

Method 2: Use non-HSPICE software to realize the shift register, and simultaneously process and generate the simulation model of the HSPICE pseudo-random code excitation source. Its implementation process is shown in Figure 2:

The shift register is implemented by non-HSPICE software; the non-HSPICE software is run to output the shift sequence; the pseudo-random code excitation source model recognized by HSPICE is generated; HSPICE calls the pseudo-random code excitation source model for simulation.

This method has the following disadvantages:

1. It is necessary to run non-HSPICE software to generate the pseudo-random code excitation source model, so the speed is slow.

2. Generating and calling the simulation model cannot be performed at the same time.

3. It needs to be processed by non-HSPICE software, resulting in high cost.

Contents of the invention

The invention provides a method for quickly generating a pseudo-random code excitation source for simulation to solve the problems of slow speed and high cost in the existing simulation process due to the need to use various software.

In order to solve the above problems, the present invention provides the following technical solutions:

A method for quickly generating a pseudo-random code excitation source for simulation, the method is:

Determine the model parameters of the fixed repetition period sequence of the pseudo-random sequence and the excitation source of the pseudo-random code;

Using the model parameters to describe the waveform of each pseudo-random code excitation source in the pseudo-random sequence to generate a description file;

The description file is directly invoked by the simulation program, and the corresponding model parameters in the description file are replaced with actual model parameter values to generate a pseudo-random code excitation source signal; and

The simulation is carried out by using the generated pseudo-random code to stimulate the source signal to stimulate the system.

in:

The model parameters of the pseudo-random code excitation source include: per-bit duration bit of the pseudo-random sequence, rising edge time tr, falling edge time tf, low-level voltage vl and high-level voltage vh.

According to the two-dimensional coordinate relationship between time and voltage, and the position of each pseudo-random code excitation source in the pseudo-random sequence, the pseudo-random code excitation is described by the segmented line segment connecting the time coordinate point and the voltage coordinate point represented by the model parameters source waveform.

The present invention has the following beneficial effects:

1. As long as the corresponding model parameters are set, the simulation model of the pseudo-random simulation excitation source can be quickly generated and called for simulation, so the speed is fast.

2. The present invention directly generates and invokes the pseudo-random code excitation source model in HSPICE without requiring other software tools, so the cost is relatively low.

Description of drawings

Fig. 1 is the simulation flowchart of prior art 1;

Fig. 2 is the simulation flowchart of prior art 2;

Fig. 3 is the simulation flowchart of the present invention;

Fig. 4 is a schematic diagram of related parameters of the pseudo-random code excitation source model of the present invention.

Detailed ways

The invention adopts the characteristics of stable repetition of pseudo-random codes in a certain period and the characteristics of direct parameterization of integrated circuit high-speed simulation software HSPICE.

Referring to shown in Figure 3, the main process of the present invention is as follows:

1. Determine the fixed repetition period sequence of the pseudo-random sequence.

Since the pseudo-random sequence has periodic and stable repetition, the sequence of the two elements "0" (ie low level) and "1" (ie high level) in the sequence can be determined. Whether the nth bit is "0" (that is, a low-level voltage) or "1" (that is, a high-level voltage) is fixed.如对于具体的(1+x3+x7)PRBS伪随机码来说，其周期固定重复序列为：1011001010110101111101111000011000100010100110011110101010001111111001000000101100000111010000100111000110100100101110110111001。 Whether the specific nth bit is "0" (that is, a low-level voltage) or "1" is fixed.

2. Set the model parameters of the pseudo-random code excitation source.

Utilizing the characteristic that HSPICE circuit can be parameterized, according to the demand of pseudo-random sequence excitation source model, the relevant parameters of pseudo-random code excitation source simulation model are proposed. The relevant parameters are shown in Figure 4, and these parameters include:

(1) Each bit time tbit of the pseudo-random sequence;

(2) The rising edge time tr, that is, the conversion time from "0" (low level) to "1" (high level);

(3) Falling edge time tf, that is, the conversion time from "1" (high level) to "0" (low level);

(4) "0" (low level) voltage vl;

(5) "1" (high level) voltage vh.

After setting the above parameters, the interface model of the pseudo-random code excitation source simulation model can be defined as:

.subckt prbs Dataout tbit＝1000ps tr＝100ps tf＝100ps vh＝1v vl＝0v

The parameters tbit=1000ps tr=100ps tf=100ps vh=1v vl=0v are the default values, which can be modified according to the actual value.

3. Using the model parameters to describe the waveform of each bit of the pseudo-random code excitation source in the pseudo-random sequence, and generate a description file of the simulation model of the pseudo-random code excitation source.

Referring to FIG. 4 , the excitation source waveform for any bit in the pseudo-random sequence can be composed of segmented curves connected with (time, voltage) coordinate points. According to the different situations of two connected bits, it is processed separately:

(1) If the "0" (low level) of the (n-1)th bit is switched to the "1" high level of the nth bit, the excitation source can use the time and voltage coordinate point [(n-1)* tbit, vl], [(n-1)*tbit+tr, vh], [n*tbit, vh] are connected to represent.

(2) If the "1" (high level) of the (n-1)th bit is switched to the "0" (low level) of the nth bit, the excitation source can use the time and voltage coordinate point [(n- 1) *tbit, vh], [(n-1)*tbit+tf, vl], [n*tbit, vl] are connected to represent.

(3) If the (n-1)th bit and the nth bit are both "0" (low level), the excitation source can use time and voltage coordinate points [(n-1)*tbit, vl], [n *tbit, vl] connected to represent.

(4) If the (n-1)th bit and the nth bit are both "1" high level, the excitation source can use the time and voltage coordinate points [(n-1)*tbit, vh], [n*tbit, vh] connected to represent.

The fixed repeating sequences in the pseudo-random sequences are represented by the methods (1) to (4) above.

The periodic repetition of the pseudo-random sequence can be done in HSPICE using the pulse function with the R parameter.

Thus, the whole pseudo-random sequence excitation source simulation model circuit with parameters is realized.

4. HSPICE directly invokes the description file, and replaces the corresponding model parameters in the description file with actual model parameter values to generate a pseudo-random code excitation source signal for simulation.

If you want to simulate the simulation model of a specific pseudo-code excitation source with a bit time tbit of 10000ps, waveform rising edge time tr of 150ps, falling edge time of 200ps, high-level voltage vh of 3V, and low-level voltage of 1V, only Need to use X_prbs Dataout prbs tbit＝10000pstr＝150ps tf＝200ps vh＝3V vl＝0V directly in HSPICE, HSPICE calls the description file and replaces the parameters with the actual value, and generates the corresponding pseudo-random code excitation according to the simulation model of the pseudo-random code excitation source The source signal by which the system is stimulated for simulation.

In the actual application of the excitation source model, as long as the steps 1-3 are done once, it can be adapted to various practical applications under different tbit, tr, tf, vh and vl parameters. That is to say, without repeating steps 1-3, HSPICE can directly generate and call pseudo-random code excitation source simulation models under different tbit, tr, tf, vh and vl parameters.

Claims (5)

1, a kind of quick generation pseudo-random code driving source carries out method of emulation, it is characterized in that this method is:

Determine the fixed repetition period sequence of pseudo-random sequence and the model parameter of pseudo-random code driving source;

Utilize described model parameter to describe the waveform of each the pseudo-random code driving source in the described pseudo-random sequence, produce the description document of pseudo-random code driving source realistic model;

Directly call described description document by simulated program, and replace corresponding model parameter generation pseudo-random code excitation source signal in this description document with actual model parameter value; And

Utilize the pseudo-random code excitation source signal excitation system that produces to carry out emulation.

2, the method for claim 1 is characterized in that, the model parameter of described pseudo-random code driving source comprises: every bit duration bit, rising edge time tr, negative edge time tf, low level voltage vl and the high level voltage vh of pseudo-random sequence.

3, method as claimed in claim 2, it is characterized in that, two-dimensional coordinate relation according to time and voltage, and each pseudo-random code driving source position in pseudo-random sequence, the segmentation line segment that the time coordinate point that utilizes model parameter to represent links to each other with voltage coordinate point is described the waveform of pseudo-random code driving source.

4, method as claimed in claim 3 is characterized in that:

If when " 0 " of n-1 position is transformed into " 1 " of n position, links to each other and describe the excitation sources waveform of n position in the described pseudo-random sequence with time and voltage coordinate point [(n-1) * tbit, vl], [(n-1) * tbit+tr, vh], [n*tbit, vh];

If when " 1 " of n-1 position is transformed into " 0 " of n position, links to each other and describe the excitation sources waveform of n position in the described pseudo-random sequence with time and voltage coordinate point [(n-1) * tbit, vh], [(n-1) * tbit+tf, vl] [n*tbit, vl];

When if n-1 position and n position all are " 0 " in the described pseudo-random sequence, use time and voltage coordinate point [(n-1) * tbit, vl], [n*tbit, vl] to link to each other and describe excitation sources waveform of n position.

When if n-1 position and n position all are " 1 " in the described pseudo-random sequence, link to each other and describe the excitation sources waveform of n position with time and voltage coordinate point [(n-1) * tbit, vh], [n*tbit, vh].

5, the method for claim 1 is characterized in that, the model parameter value of described reality can or adopt default value by manual input.

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