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MCUXpresso SDK API Reference Manual
Rev 2.12.1
NXP Semiconductors
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MCUXpresso SDK API Reference Manual
Rev 2.12.1
NXP Semiconductors
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The MCUXpresso SDK provides a peripheral driver for the Cyclic Redundancy Check (CRC) module of MCUXpresso SDK devices.
The cyclic redundancy check (CRC) module generates 16/32-bit CRC code for error detection. The CRC module also provides a programmable polynomial, seed, and other parameters required to implement a 16-bit or 32-bit CRC standard.
CRC_Init() function enables the clock gate for the CRC module in the SIM module and fully (re-)configures the CRC module according to the configuration structure. The seed member of the configuration structure is the initial checksum for which new data can be added to. When starting a new checksum computation, the seed is set to the initial checksum per the CRC protocol specification. For continued checksum operation, the seed is set to the intermediate checksum value as obtained from previous calls to CRC_Get16bitResult() or CRC_Get32bitResult() function. After calling the CRC_Init(), one or multiple CRC_WriteData() calls follow to update the checksum with data and CRC_Get16bitResult() or CRC_Get32bitResult() follow to read the result. The crcResult member of the configuration structure determines whether the CRC_Get16bitResult() or CRC_Get32bitResult() return value is a final checksum or an intermediate checksum. The CRC_Init() function can be called as many times as required allowing for runtime changes of the CRC protocol.
CRC_GetDefaultConfig() function can be used to set the module configuration structure with parameters for CRC-16/CCIT-FALSE protocol.
The CRC_WriteData() function adds data to the CRC. Internally, it tries to use 32-bit reads and writes for all aligned data in the user buffer and 8-bit reads and writes for all unaligned data in the user buffer. This function can update the CRC with user-supplied data chunks of an arbitrary size, so one can update the CRC byte by byte or with all bytes at once. Prior to calling the CRC configuration function CRC_Init() fully specifies the CRC module configuration for the CRC_WriteData() call.
The CRC_Get16bitResult() or CRC_Get32bitResult() function reads the CRC module data register. Depending on the prior CRC module usage, the return value is either an intermediate checksum or the final checksum. For example, for 16-bit CRCs the following call sequences can be used.
CRC_Init() / CRC_WriteData() / CRC_Get16bitResult() to get the final checksum.
CRC_Init() / CRC_WriteData() / ... / CRC_WriteData() / CRC_Get16bitResult() to get the final checksum.
CRC_Init() / CRC_WriteData() / CRC_Get16bitResult() to get an intermediate checksum.
CRC_Init() / CRC_WriteData() / ... / CRC_WriteData() / CRC_Get16bitResult() to get an intermediate checksum.
If multiple RTOS tasks share the CRC module to compute checksums with different data and/or protocols, the following needs to be implemented by the user.
The triplets
CRC_Init() / CRC_WriteData() / CRC_Get16bitResult() or CRC_Get32bitResult()
The triplets are protected by the RTOS mutex to protect the CRC module against concurrent accesses from different tasks. This is an example. Refer to the driver examples codes located at <SDK_ROOT>/boards/<BOARD>/driver_examples/crcRefer to the driver examples codes located at <SDK_ROOT>/boards/<BOARD>/driver_examples/crcRefer to the driver examples codes located at <SDK_ROOT>/boards/<BOARD>/driver_examples/crcRefer to the driver examples codes located at <SDK_ROOT>/boards/<BOARD>/driver_examples/crcRefer to the driver examples codes located at <SDK_ROOT>/boards/<BOARD>/driver_examples/crc
Data Structures | |
| struct | crc_config_t |
| CRC protocol configuration. More... | |
Macros | |
| #define | CRC_DRIVER_USE_CRC16_CCIT_FALSE_AS_DEFAULT 1 |
| Default configuration structure filled by CRC_GetDefaultConfig(). More... | |
Enumerations | |
| enum | crc_bits_t { kCrcBits16 = 0U, kCrcBits32 = 1U } |
| CRC bit width. More... | |
| enum | crc_result_t { kCrcFinalChecksum = 0U, kCrcIntermediateChecksum = 1U } |
| CRC result type. More... | |
Functions | |
| void | CRC_Init (CRC_Type *base, const crc_config_t *config) |
| Enables and configures the CRC peripheral module. More... | |
| static void | CRC_Deinit (CRC_Type *base) |
| Disables the CRC peripheral module. More... | |
| void | CRC_GetDefaultConfig (crc_config_t *config) |
| Loads default values to the CRC protocol configuration structure. More... | |
| void | CRC_WriteData (CRC_Type *base, const uint8_t *data, size_t dataSize) |
| Writes data to the CRC module. More... | |
| uint32_t | CRC_Get32bitResult (CRC_Type *base) |
| Reads the 32-bit checksum from the CRC module. More... | |
| uint16_t | CRC_Get16bitResult (CRC_Type *base) |
| Reads a 16-bit checksum from the CRC module. More... | |
Driver version | |
| #define | FSL_CRC_DRIVER_VERSION (MAKE_VERSION(2, 0, 3)) |
| CRC driver version. More... | |
| struct crc_config_t |
This structure holds the configuration for the CRC protocol.
Data Fields | |
| uint32_t | polynomial |
| CRC Polynomial, MSBit first. More... | |
| uint32_t | seed |
| Starting checksum value. | |
| bool | reflectIn |
| Reflect bits on input. More... | |
| bool | reflectOut |
| Reflect bits on output. More... | |
| bool | complementChecksum |
| True if the result shall be complement of the actual checksum. More... | |
| crc_bits_t | crcBits |
| Selects 16- or 32- bit CRC protocol. More... | |
| crc_result_t | crcResult |
| Selects final or intermediate checksum return from CRC_Get16bitResult() or CRC_Get32bitResult() | |
| uint32_t crc_config_t::polynomial |
Example polynomial: 0x1021 = 1_0000_0010_0001 = x^12+x^5+1
| bool crc_config_t::reflectIn |
| bool crc_config_t::reflectOut |
| bool crc_config_t::complementChecksum |
| crc_bits_t crc_config_t::crcBits |
| #define FSL_CRC_DRIVER_VERSION (MAKE_VERSION(2, 0, 3)) |
Version 2.0.3.
Current version: 2.0.3
Change log:
| #define CRC_DRIVER_USE_CRC16_CCIT_FALSE_AS_DEFAULT 1 |
Use CRC16-CCIT-FALSE as defeault.
| enum crc_bits_t |
| enum crc_result_t |
| Enumerator | |
|---|---|
| kCrcFinalChecksum |
CRC data register read value is the final checksum. Reflect out and final xor protocol features are applied. |
| kCrcIntermediateChecksum |
CRC data register read value is intermediate checksum (raw value). Reflect out and final xor protocol feature are not applied. Intermediate checksum can be used as a seed for CRC_Init() to continue adding data to this checksum. |
| void CRC_Init | ( | CRC_Type * | base, |
| const crc_config_t * | config | ||
| ) |
This function enables the clock gate in the SIM module for the CRC peripheral. It also configures the CRC module and starts a checksum computation by writing the seed.
| base | CRC peripheral address. |
| config | CRC module configuration structure. |
|
inlinestatic |
This function disables the clock gate in the SIM module for the CRC peripheral.
| base | CRC peripheral address. |
| void CRC_GetDefaultConfig | ( | crc_config_t * | config | ) |
Loads default values to the CRC protocol configuration structure. The default values are as follows.
| config | CRC protocol configuration structure. |
| void CRC_WriteData | ( | CRC_Type * | base, |
| const uint8_t * | data, | ||
| size_t | dataSize | ||
| ) |
Writes input data buffer bytes to the CRC data register. The configured type of transpose is applied.
| base | CRC peripheral address. |
| data | Input data stream, MSByte in data[0]. |
| dataSize | Size in bytes of the input data buffer. |
| uint32_t CRC_Get32bitResult | ( | CRC_Type * | base | ) |
Reads the CRC data register (either an intermediate or the final checksum). The configured type of transpose and complement is applied.
| base | CRC peripheral address. |
| uint16_t CRC_Get16bitResult | ( | CRC_Type * | base | ) |
Reads the CRC data register (either an intermediate or the final checksum). The configured type of transpose and complement is applied.
| base | CRC peripheral address. |
