CRC (Cyclic Redundancy Check)

group group_hal_crc

High level interface for interacting with the CRC, which provides hardware accelerated CRC computations.

The CRC APIs are structured to enable usage in situations where the entire input data set is not available in memory at the same time. Therefore, each conversion consists of three steps:

The table below provides CRC parameters for some common CRC algorithms.

note

The Expected CRC column shows the computed CRC when the value "123456789" is passed to cyhal_crc_compute.

CRC algorithm Name

Len

Polynomial

Initial seed

Data REV

Data XOR

Rem REV

Remainder XOR

Expected CRC

CRC-6 / CDMA2000-A

6

0x27

0x3F

false

0

false

0x00

0x0D

CRC-6 / CDMA2000-B

6

0x07

0x3F

false

0

false

0x00

0x3B

CRC-6 / DARC

6

0x19

0x00

true

0

true

0x00

0x26

CRC-6 / ITU

6

0x03

0x00

true

0

true

0x00

0x06

CRC-8 / ITU

8

0x07

0x00

false

0

false

0x55

0xA1

CRC-8 / MAXIM

8

0x31

0x00

true

0

true

0x00

0xA1

CRC-8 / ROHC

8

0x07

0xFF

true

0

true

0x00

0xD0

CRC-8 / WCDMA

8

0x9B

0x00

true

0

true

0x00

0x25

CRC-16 / CCITT-0

16

0x1021

0xFFFF

false

0

false

0x0000

0x29B1

CRC-16 / CDMA2000

16

0xC867

0xFFFF

false

0

false

0x0000

0x4C06

CRC-32

32

0x04C11DB7

0xFFFFFFFF

true

0

true

0xFFFFFFFF

0xCBF43926

CRC-32 / BZIP2

32

0x04C11DB7

0xFFFFFFFF

false

0

false

0xFFFFFFFF

0xFC891918

note

Algorithms that have less than 8 bits, like CRC-6, populate the lower bits and leave the high order bits 0.

note

Many of the algorithm parameters can be customized.

See

crc_algorithm_t and Snippet1: CRC Generation for more details.

Quick Start

cyhal_crc_init initializes the CRC generator and passes the pointer to the CRC block through the obj object of type cyhal_crc_t.

Snippet1: CRC Generation

The following snippet initializes a CRC generator and computes the CRC for a sample message.


    // Using CRC-16/CCITT-0 Algorithm
    #define CRC_BITLEN          (16u)
    #define CRC_POLYNOMIAL      (0x1021u)
    #define CRC_LFSR_SEED       (0xffffu)
    #define CRC_DATA_REVERSE    (0u)
    #define CRC_DATA_XOR        (0u)
    #define CRC_REM_REVERSE     (0u)
    #define CRC_REM_XOR         (0x0000u)

    #define MSG_LENGTH 9

    CY_ALIGN(4) uint8_t message[MSG_LENGTH] = "123456789";
    CY_ALIGN(4) uint32_t calc_crc           = 0;

    // Set CRC algorithm parameters
    crc_algorithm_t my_algorithm =
    {
        .width         = CRC_BITLEN,
        .polynomial    = CRC_POLYNOMIAL,
        .lfsrInitState = CRC_LFSR_SEED,
        .dataReverse   = CRC_DATA_REVERSE,
        .dataXor       = CRC_DATA_XOR,
        .remReverse    = CRC_REM_REVERSE,
        .remXor        = CRC_REM_XOR
    };

    cy_rslt_t   rslt;
    cyhal_crc_t crc_obj;

    // Initialize the CRC Generator
    rslt = cyhal_crc_init(&crc_obj);

    // Initialize the CRC algorithm parameters
    rslt = cyhal_crc_start(&crc_obj, &my_algorithm);

    // Compute CRC
    rslt = cyhal_crc_compute(&crc_obj, message, MSG_LENGTH);

    // Finish computation
    rslt = cyhal_crc_finish(&crc_obj, &calc_crc);

    // Additional computations can be done here if needed

    // Release the CRC generator
    // Note: Free only if not required anymore
    cyhal_crc_free(&crc_obj);

Functions

cy_rslt_t cyhal_crc_init(cyhal_crc_t *obj)

Initialize the CRC generator.

This function reserves the CRYPTO block for CRC calculations.

Returns

CY_RSLT_SUCCESS if the operation was successful. Refer Snippet1: CRC Generation for more information.
Return

The status of the init request.

Parameters

  • [out] obj: Pointer to a CRC generator object. The caller must allocate the memory for this object but the init function will initialize its contents.

void cyhal_crc_free(cyhal_crc_t *obj)

Release the CRC generator.

Parameters

  • [inout] obj: The CRC generator object

cy_rslt_t cyhal_crc_start(cyhal_crc_t *obj, const crc_algorithm_t *algorithm)

The CRC block is setup to perform CRC computation.

note

The state of the CRC Block will be reset to the state provided by in the argument algorithm.

Returns

CY_RSLT_SUCCESS if the operation was successful.
Return

The status of the compute request

Parameters

  • [inout] obj: The CRC generator object

  • [in] algorithm: The CRC algorithm to use for computations Refer crc_algorithm_t.

cy_rslt_t cyhal_crc_compute(const cyhal_crc_t *obj, const uint8_t *data, size_t length)

Computes the CRC for the given data and accumulates the CRC with the CRC generated from previous calls.

This function can be called multiple times to provide additional data.

note

Input data must be 4-byte aligned. Refer Snippet1: CRC Generation for more details.

Returns

CY_RSLT_SUCCESS if the operation was successful.
Return

The status of the compute request

Parameters

  • [in] obj: The CRC generator object

  • [in] data: The input data

  • [in] length: The number of bytes in the data

cy_rslt_t cyhal_crc_finish(const cyhal_crc_t *obj, uint32_t *crc)

Finalizes the CRC computation and returns the CRC for the complete set of data passed through a single call or multiple calls to cyhal_crc_compute.

note

The computed CRC pointer provided must be 4 byte aligned. Refer to Snippet1: CRC Generation for more details.

note

If the length of the CRC is less than a full word, the result will be in the lower bits allowing the result to be downcast if desired.

Returns

CY_RSLT_SUCCESS if the operation was successful.
Return

The status of the compute request

Parameters

  • [in] obj: The CRC generator object

  • [out] crc: The computed CRC

struct crc_algorithm_t
#include <cyhal_crc.h>

CRC algorithm parameters.

Public Members

uint32_t width

Bit width of the CRC.

uint32_t polynomial

The polynomial to use.

uint32_t lfsrInitState

Initial state of the LFSR.

uint32_t dataXor

Byte mask to xor with the data.

uint32_t remXor

Mask to xor with the remainder.

bool dataReverse

The order in which data should be processed.

If 0, data is processed MSB first. If 1, data is processed LSB first.

bool remReverse

If 1, the remainder is reversed. If 0, it is not.