crc.generator

(To be removed) Construct CRC generator object

crc.generator will be removed in a future release. To generate cyclic redundancy check (CRC) code bits, use the comm.CRCGenerator System object instead. For more details on the recommended workflow, see Compatibility Considerations.

Syntax

h = crc.generator(polynomial)

h = crc.generator(detectorObj)

h = crc.generator(‘Polynomial’, polynomial, ‘param1’, val1, etc.)

h = crc.generator

Description

h = crc.generator(polynomial) constructs a CRC generator object H defined by the generator polynomial POLYNOMIAL.

h = crc.generator(detectorObj) constructs a CRC generator object H defined by the parameters found in the CRC detector object DETECTOROBJ.

h = crc.generator(‘property1', val1, ...) constructs a CRC generator object H with properties as specified by the PROPERTY/VALUE pairs.

h = crc.generator constructs a CRC generator object H with default properties. It constructs a CRC-CCITT generator, and is equivalent to: h = crc.generator('Polynomial', '0x1021', 'InitialState', '0xFFFF', ...

'ReflectInput', false, 'ReflectRemainder', false, 'FinalXOR', '0x0000').

Properties

The following table describes the properties of a CRC generator object. All properties are writable, except Polynomial.

Property	Description
Polynomial	The generator polynomial that defines connections for a linear feedback shift register. This property can be specified as a binary vector representing descending powers of the polynomial. In this case, the leading '1' of the polynomial must be included. It can also be specified as a string, prefaced by '0x', that is a hexadecimal representation of the descending powers of the polynomial. In this case, the leading '1' of the polynomial is omitted.
InitialState	The initial contents of the shift register. This property can be specified as a binary scalar, a binary vector, or as a string, prefaced by '0x', that is a hexadecimal representation of the binary vector. As a binary vector, its length must be one less than the length of the binary vector representation of the Polynomial.
ReflectInput	A Boolean quantity that specifies whether the input data should be flipped on a bytewise basis prior to entering the shift register.
ReflectRemainder	A Boolean quantity that specifies whether the binary output CRC checksum should be flipped around its center after the input data is completely through the shift register.
FinalXOR	The value with which the CRC checksum is to be XORed just prior to being appended to the input data. This property can be specified as a binary scalar, a binary vector, or as a string, prefaced by '0x', that is a hexadecimal representation of the binary vector. As a binary vector, its length must be one less than the length of the binary vector representation of the Polynomial.

CRC Generation Algorithm

For information pertaining to the CRC generation algorithm, refer to the CRC Non-Direct Algorithm section of the Communications Toolbox™ User's Guide.

Generator Method

encoded = generate(h, msg) generates a CRC checksum for an input message using the CRC generator object H. It appends the checksum to the end of MSG. The binary-valued MSG can be either a column vector or a matrix. If it is a matrix, then each column is considered to be a separate channel.

Examples

Create a CRC-16 CRC generator, then use it to generate a checksum for the binary vector represented by the ASCII sequence '123456789'.

gen = crc.generator('Polynomial', '0x8005', ...
'ReflectInput', true, 'ReflectRemainder', true);

The message below is an ASCII representation of the digits 1-9.

msg = reshape(de2bi(49:57, 8, 'left-msb')', 72, 1);
encoded = generate(gen, msg);

h = 

                Type: CRC Generator
          Polynomial: 0xF
        InitialState: 0xF
        ReflectInput: true
    ReflectRemainder: false
            FinalXOR: 0x0

Compatibility Considerations

crc.generator will be removed in a future release.

Warns starting in R2020b

crc.generator will be removed in a future release. To generate cyclic redundancy check (CRC) code, use the comm.CRCGenerator System object instead.

Replace instances of crc.generator with a comm.CRCGenerator System object. Note the mapping between crc.generator properties and comm.CRCGenerator properties:

crc.generator	comm.CRCGenerator
Polynomial	Polynomial
InitialState	InitialConditions
ReflectInput	ReflectInputBytes
ReflectRemainder	Reflectchecksums
FinalXOR	FinalXOR

See the following table for examples of migrating the old workflow to the recommended workflow.

Previous Workflow	Recommended Workflow
data = randi([0 1],100,1); oldO = crc.generator encOld = generate(oldO,data); oldO = Type: CRC Generator Polynomial: 0x1021 InitialState: 0xFFFF ReflectInput: false ReflectRemainder: false FinalXOR: 0x0000	data = randi([0 1],100,1); sysO = comm.CRCGenerator('InitialConditions',1) encNew = sysO(data); sysO = comm.CRCGenerator with properties: Polynomial: 'z^16 + z^12 + z^5 + 1' InitialConditions: 1 DirectMethod: false ReflectInputBytes: false ReflectChecksums: false FinalXOR: 0 ChecksumsPerFrame: 1
data = randi([0 1],96,1); oldO = crc.generator('Polynomial', '0xF', 'InitialState', '0xF',... 'ReflectInput', true, 'FinalXOR', '0x0') encOld = generate(oldO,data); Type: CRC Generator Polynomial: 0xF InitialState: 0xF ReflectInput: true ReflectRemainder: false FinalXOR: 0x0	data = randi([0 1],96,1); sysO = comm.CRCGenerator('Polynomial',... '0x1F','InitialConditions', [1 1 1 1],... 'ReflectInputBytes', true, 'FinalXOR', 0) encNew = sysO(data); sysO = comm.CRCGenerator with properties: Polynomial: '0x1F' InitialConditions: [1 1 1 1] DirectMethod: false ReflectInputBytes: true ReflectChecksums: false FinalXOR: 0 ChecksumsPerFrame: 1
data = randi([0 1],100,5); oldO = crc.generator([1 1 1 1 1]) encOld = generate(oldO,data); oldO = Type: CRC Generator Polynomial: 0xF InitialState: 0x0 ReflectInput: false ReflectRemainder: false FinalXOR: 0x0	data = randi([0 1],100,5); sysO = comm.CRCGenerator('Polynomial',[1 1 1 1 1],... 'ChecksumsPerFrame',5) encNew = sysO(data(:)); sysO = comm.CRCGenerator with properties: Polynomial: [1 1 1 1 1] InitialConditions: 0 DirectMethod: false ReflectInputBytes: false ReflectChecksums: false FinalXOR: 0 ChecksumsPerFrame: 5