Scramble input signal

Sequence Operations

The Scrambler block scrambles a scalar or column vector input
signal. If you set the **Calculation base** parameter
to *N*, then the input values must be integers between
0 and N-1.

One purpose of scrambling is to reduce the length of strings
of 0s or 1s in a transmitted signal, since a long string of 0s or
1s may cause transmission synchronization problems. Below is a schematic
of the scrambler. All adders perform addition modulo *N*.

At each time step, the input causes the contents of the registers
to shift sequentially. The **Scramble polynomial** parameter
defines if each switch in the scrambler is on or off. Specify the
polynomial as a string, for example, ```
'1
+ z^-6 + z^-8'
```

. Alternatively, you can specify the polynomial
by listing its coefficients in order of ascending powers of *z*^{-1},
where *p*(*z*^{-1})
= 1 + *p _{1}z*

The **Initial states** parameter lists the
states of the scrambler's registers when the simulation starts. The
elements of this vector must be integers between 0 and *N*-1.
The vector length of this parameter must equal the order of the scramble
polynomial. (If the **Scramble polynomial** parameter
is a vector that lists the coefficients in order, then the order of
the scramble polynomial is one less than the vector length). There
is an optional port that can be used to reset the scrambler.

Alternatively, the initial states can be provided by an input
port when **Initial states source** parameter is
set to `Input port`

.

This block can accept input sequences that vary in length during
simulation. For more information about sequences that vary in length,
or variable-size signals, see Variable-Size Signal Basics in the Simulink^{®} documentation.

**Calculation base**The calculation base N. The input and output of this block are integers in the range [0, N-1].

**Scramble polynomial**A polynomial that defines the connections in the scrambler.

**Initial states source**A drop down menu that controls the source of the initial states. Select either

`Dialog Parameter`

or`Input port`

. The default value is`Dialog Parameter`

.**Initial states**The states of the scrambler's registers when the simulation starts. This parameter is available when

**Initial states source**is set to`Dialog Parameter`

.**Reset on nonzero input via port**A check box that creates a reset port. When checked, the scrambler is reset if a nonzero input is applied to the port. This control is available when

**Initial states source**is set to`Dialog Parameter`

. The default is that the box is not checked.

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