## Description

`Y = step(H,X)`

decodes input binary codewords
in `X`

using a (`CodewordLength`

,`MessageLength`

)
BCH decoder with the corresponding narrow-sense generator polynomial.
The step method returns the estimated message in `Y`

.
This syntax applies when you set the `NumCorrectedErrorsOutputPort`

property
to false. The input and output length of the step function equal the
values listed in the table in Input and Output Signal Lengths in BCH and RS System Objects.

`[Y,ERR] = step(H,X)`

returns the number
of corrected errors in output `ERR`

when you set
the `NumCorrectedErrorsOutputPort`

property to `true`

.
A non- negative value in the *i*-th element of the `ERR`

output
vector denotes the number of corrected errors in the *i*-th
input codeword. A value of `-1`

in the *i*-th
element of the `ERR`

output indicates that a decoding
error occurred for the *i*-th input codeword. A decoding
error occurs when an input codeword has more errors than the error
correction capability of the BCH code.

`Y = step(H,X,ERASURES)`

uses `ERASURES`

as
the erasures pattern input when you set the `ErasuresInputPort`

property
to `true`

. The object decodes the binary encoded
data input, `X`

, and treats as erasures the bits
of the input codewords specified by the binary column vector, `ERASURES`

.
The length of `ERASURES`

must equal the length of `X`

,
and its elements must be of data type double or logical. Values of `1`

in
the erasures vector correspond to erased bits in the same position
of the (possibly punctured) input codewords.

**Note:**
`H` specifies the System object™ on which
to run this `step` method.
The object performs an initialization the first time the `step` method
is executed. This initialization locks nontunable
properties and input specifications, such as dimensions,
complexity, and data type of the input data. If you change a nontunable
property or an input specification, the System object issues an
error. To change nontunable properties or inputs, you must first call
the `release` method to unlock the object. |