# Documentation

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# step

System object: comm.CRCGenerator
Package: comm

Generate CRC code bits and append to input data

## Syntax

`Y = step(H,X)`

## Description

 Note:   Starting in R2016b, instead of using the `step` method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, `y = step(obj,x)` and `y = obj(x)` perform equivalent operations.

`Y = step(H,X)` generates CRC checksums for an input message `X` and appends the checksums to `X`. The input `X` must be a binary column vector and the data type can be double or logical. The length of output `Y` is length(`X`) + P$×$`CheckSumsPerFrame`, where P is the order of the polynomial that you specify in the `Polynomial` property.

 Note:   `obj` 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 (MATLAB) 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.