The pseudo-random bit sequence (PRBS) generator a maximum length sequence code using a random initial state
Keywords
digital, unidirectional
Ports
| Name | Type |
|---|---|
| output | Digital Signal |
Properties
General Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
name Defines the name of the element. |
PRBS Generator | - | - |
|
annotate Defines whether or not to display annotations on the schematic editor. |
true | - | [true, false] |
|
enabled Defines whether or not the element is enabled. |
true | - | [true, false] |
|
type Defines the element unique type (read only). |
PRBS Generator | - | - |
|
description A brief description of the elements functionality. |
The pseudo-random bit sequence (PRBS) generator a maximum length sequence code using a random initial state | - | - |
|
prefix Defines the element name prefix. |
PRBS | - | - |
|
model Defines the element model name. |
- | - | - |
|
library Defines the element location or source in the library (custom or design kit). |
- | - | - |
|
local path Defines the local path or working folder $LOCAL for the element. |
- | - | - |
|
url An optional URL address pointing to the element online help. |
- | - | - |
Standard Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
bitrate The output signal bitrate. |
%bitrate% | bits/s | [1, +∞) |
|
output Defines the output type or the operation mode of the generator. |
PRBS | - | [PRBS, zeros, ones, alternate, codeword, load from file |
|
order The polynomial order for the PRBS signal for 'PRBS' output type configuration. |
log(%sequence length%)/log(2) | - | [1, 32] |
|
codeword The user defined codeword for 'codeword' output type configuration. |
101010101010 | - | - |
|
measurement filename The filename containing the bit sequence for 'load from file' output type configuration. Input file is formatted without any headers and it should contain the bit values only, one value per line. |
pattern.dat | - | - |
Numerical Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
automatic seed Defines whether or not to automatically create an unique seed value for each instance of this element. The seed will be the same for each simulation run. |
true | - | [true, false] |
|
seed The value of the seed for the random number generator. A value zero recreates an unique seed for each simulation run. |
1 | - | [0, +∞) |
Simulation Properties
| Name | Default value | Default unit | Range |
|---|---|---|---|
|
output signal mode The output signal mode. |
%output signal mode% | - | [sample, block |
|
number of output signals The number of simulation runs, or the number of generated signals. |
%number of output signals% | - | [1, +∞) |
|
time window The duration of the generated signal. This is typically set by the global properties in the root (top-most) element. |
%time window% | s | (0, +∞) |
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Implementation Details
The pseudo-random bit sequence generator could generate a bit stream with the format according to the setting. The bit rate by default is inherited from the root element setting but could be re-defined by setting the bitrate "Expression" to none. The generated sequence length could be pre-set in the root element. The following figure shows the system in the example file PRBS.icp.
There are six formats that can be chosen from for the sequence generated. Following is the setting for the output.
When "PRBS" is chosen, the pseudo-random bit stream is generated; "automatic seed" under the "Numerical" setting can be set to be "true" for a random grabbing of the bit sequence seed or "false" for a desired bit sequence seed which is pre-defined in the software. The "order" under the "Standard" setting indicates the sequence length in the power of 2.
When "zeros" or "ones" are chosen for the output, a sequence of 0s/1s are generated. When "alternate" is chosen, a bit stream of alternated 0s and 1s are generated starting from the bit 0.
When "codeword" is chosen, the "codeword" setting is enabled, user can directly type in the bit sequence in the setting frame. However, when the number of bits defined in the "codeword" is less than the sequence length setting in the root element, the bit stream will repeat itself until the number of bits reaches the setting sequence length; when the number of bits defined in the "codeword" is larger than the sequence length setting, the bit sequence will be truncated at the setting length.
When "load from file" is chosen, a data file can be input to the system. Please see the example data file pattern.dat for more information. Note that the length of the bit stream in the file will be adjusted the same way as in the "codeword" to fit the sequence length.
The following figure is plotted by the Logic Analyzer LGCA_1, when the output is set to "PRBS". For more information of the Logic Analyzer, please see the element library page Logic Analyzer.