Macros
#define	CRC8_ITER(crc, data) g_pui8Crc8CCITT[(uint8_t)((crc) ^ (data))]

#define	CRC16_ITER(crc, data)

#define	CRC32_ITER(crc, data)

Functions
uint8_t	Crc8CCITT (uint8_t ui8Crc, const uint8_t *pui8Data, uint32_t ui32Count)

uint16_t	Crc16 (uint16_t ui16Crc, const uint8_t *pui8Data, uint32_t ui32Count)

uint16_t	Crc16Array (uint32_t ui32WordLen, const uint32_t *pui32Data)

void	Crc16Array3 (uint32_t ui32WordLen, const uint32_t pui32Data, uint16_t pui16Crc3)

uint32_t	Crc32 (uint32_t ui32Crc, const uint8_t *pui8Data, uint32_t ui32Count)

Detailed Description

Introduction

The CRC module provides functions to compute the CRC-8-CCITT and CRC-16 of a buffer of data. Support is provided for computing a running CRC, where a partial CRC is computed on one portion of the data, and then continued at a later time on another portion of the data. A running CRC is useful when computing the CRC on a stream of data that is coming in via a serial link for example).

A CRC is useful for detecting errors that occur during the transmission of data over a communications channel or during storage in a memory (such as flash). However, a CRC does not provide protection against an intentional modification or tampering of the data.

Programming Example

The following example shows how to compute the CRC-16 of a buffer of data.

unsigned long ulIdx, ulValue;
unsigned char pucData[256];
//
// Fill pucData with some data.
//
for(ulIdx = 0; ulIdx < 256; ulIdx++)
{
    pucData[ulIdx] = ulIdx;
}
//
// Compute the CRC-16 of the data.
//
ulValue = Crc16(0, pucData, 256);

Macro Definition Documentation

§ CRC8_ITER

#define CRC8_ITER	(	crc,
		data
	)	g_pui8Crc8CCITT[(uint8_t)((crc) ^ (data))]

Referenced by Crc8CCITT().

§ CRC16_ITER

#define CRC16_ITER	(	crc,
		data
	)

Value:

(((crc) >> 8) ^ \

g_pui16Crc16[(uint8_t)((crc) ^ (data))])

Referenced by Crc16(), and Crc16Array3().

§ CRC32_ITER

#define CRC32_ITER	(	crc,
		data
	)

Value:

(((crc) >> 8) ^                               \
                                 g_pui32Crc32[(uint8_t)((crc & 0xFF) ^        \
                                                        (data))])

Referenced by Crc32().

Function Documentation

§ Crc8CCITT()

uint8_t Crc8CCITT	(	uint8_t	ui8Crc,
		const uint8_t *	pui8Data,
		uint32_t	ui32Count
	)

Calculates the CRC-8-CCITT of an array of bytes.

Parameters

ui8Crc	is the starting CRC-8-CCITT value.
pui8Data	is a pointer to the data buffer.
ui32Count	is the number of bytes in the data buffer.

This function is used to calculate the CRC-8-CCITT of the input buffer. The CRC-8-CCITT is computed in a running fashion, meaning that the entire data block that is to have its CRC-8-CCITT computed does not need to be supplied all at once. If the input buffer contains the entire block of data, then ui8Crc should be set to 0. If, however, the entire block of data is not available, then ui8Crc should be set to 0 for the first portion of the data, and then the returned value should be passed back in as ui8Crc for the next portion of the data.

For example, to compute the CRC-8-CCITT of a block that has been split into three pieces, use the following:

//!     ui8Crc = Crc8CCITT(0, pui8Data1, ui32Len1);
//!     ui8Crc = Crc8CCITT(ui8Crc, pui8Data2, ui32Len2);
//!     ui8Crc = Crc8CCITT(ui8Crc, pui8Data3, ui32Len3);
//!

Computing a CRC-8-CCITT in a running fashion is useful in cases where the
data is arriving via a serial link (for example) and is therefore not all
available at one time.

\return The CRC-8-CCITT of the input data.

References CRC8_ITER.

§ Crc16()

uint16_t Crc16	(	uint16_t	ui16Crc,
		const uint8_t *	pui8Data,
		uint32_t	ui32Count
	)

Calculates the CRC-16 of an array of bytes.

Parameters

ui16Crc	is the starting CRC-16 value.
pui8Data	is a pointer to the data buffer.
ui32Count	is the number of bytes in the data buffer.

This function is used to calculate the CRC-16 of the input buffer. The CRC-16 is computed in a running fashion, meaning that the entire data block that is to have its CRC-16 computed does not need to be supplied all at once. If the input buffer contains the entire block of data, then ui16Crc should be set to 0. If, however, the entire block of data is not available, then ui16Crc should be set to 0 for the first portion of the data, and then the returned value should be passed back in as ui16Crc for the next portion of the data.

For example, to compute the CRC-16 of a block that has been split into three pieces, use the following:

//!     ui16Crc = Crc16(0, pui8Data1, ui32Len1);
//!     ui16Crc = Crc16(ui16Crc, pui8Data2, ui32Len2);
//!     ui16Crc = Crc16(ui16Crc, pui8Data3, ui32Len3);
//!

Computing a CRC-16 in a running fashion is useful in cases where the data
is arriving via a serial link (for example) and is therefore not all
available at one time.

\return The CRC-16 of the input data.

References CRC16_ITER.

Referenced by Crc16Array().

§ Crc16Array()

uint16_t Crc16Array	(	uint32_t	ui32WordLen,
		const uint32_t *	pui32Data
	)

Calculates the CRC-16 of an array of words.

Parameters

ui32WordLen	is the length of the array in words (the number of bytes divided by 4).
pui32Data	is a pointer to the data buffer.

This function is a wrapper around the running CRC-16 function, providing the CRC-16 for a single block of data.

Returns: The CRC-16 of the input data.

References Crc16().

§ Crc16Array3()

void Crc16Array3	(	uint32_t	ui32WordLen,
		const uint32_t *	pui32Data,
		uint16_t *	pui16Crc3
	)

Calculates three CRC-16s of an array of words.

Parameters

ui32WordLen	is the length of the array in words (the number of bytes divided by 4).
pui32Data	is a pointer to the data buffer.
pui16Crc3	is a pointer to an array in which to place the three CRC-16 values.

This function is used to calculate three CRC-16s of the input buffer; the first uses every byte from the array, the second uses only the even-index bytes from the array (in other words, bytes 0, 2, 4, etc.), and the third uses only the odd-index bytes from the array (in other words, bytes 1, 3, 5, etc.).

Returns: None

References CRC16_ITER.

§ Crc32()

uint32_t Crc32	(	uint32_t	ui32Crc,
		const uint8_t *	pui8Data,
		uint32_t	ui32Count
	)

Calculates the CRC-32 of an array of bytes.

Parameters

ui32Crc	is the starting CRC-32 value.
pui8Data	is a pointer to the data buffer.
ui32Count	is the number of bytes in the data buffer.

This function is used to calculate the CRC-32 of the input buffer. The CRC-32 is computed in a running fashion, meaning that the entire data block that is to have its CRC-32 computed does not need to be supplied all at once. If the input buffer contains the entire block of data, then ui32Crc should be set to 0xFFFFFFFF. If, however, the entire block of data is not available, then ui32Crc should be set to 0xFFFFFFFF for the first portion of the data, and then the returned value should be passed back in as ui32Crc for the next portion of the data. Once all data has been passed to the function, the final CRC-32 can be obtained by inverting the last returned value.

For example, to compute the CRC-32 of a block that has been split into three pieces, use the following:

//!     ui32Crc = Crc32(0xFFFFFFFF, pui8Data1, ui32Len1);
//!     ui32Crc = Crc32(ui32Crc, pui8Data2, ui32Len2);
//!     ui32Crc = Crc32(ui32Crc, pui8Data3, ui32Len3);
//!     ui32Crc ^= 0xFFFFFFFF;
//!

Computing a CRC-32 in a running fashion is useful in cases where the data
is arriving via a serial link (for example) and is therefore not all
available at one time.

\return The accumulated CRC-32 of the input data.

References CRC32_ITER.

Referenced by EMACHashFilterBitCalculate(), and EMACVLANHashFilterBitCalculate().

Macros

Functions

Detailed Description

Introduction

Programming Example

Macro Definition Documentation

§ CRC8_ITER

§ CRC16_ITER

§ CRC32_ITER

Function Documentation

§ Crc8CCITT()

§ Crc16()

§ Crc16Array()

§ Crc16Array3()

§ Crc32()