sd_card_crc

Author	AI Assistant
Adapted-by
Compiler	>=2.4q3

Description

This library provides CRC7 and CRC16 calculations for SD card
             communication in SPI mode. CRC7 is used for command frames,
             CRC16 is used for data blocks.

Sources

SD Card Physical Layer Simplified Specification Version 2.00
SanDisk Secure Digital Card - http://www.cs.ucr.edu/~amitra/sdcard/ProdManualSDCardv1.9.pdf

Notes

- CRC7 polynomial: x^7 + x^3 + 1 (0x89)
- CRC16 polynomial: x^16 + x^12 + x^5 + 1 (0x1021)
- CRC7 is used for SD card command frames
- CRC16 is used for SD card data blocks

Dependencies

No dependency found

Summary

Global variables/contants

• const byte CRC_ERROR_VERIFICATION_FAILED = 3
• const byte CRC_ERROR_NONE = 0
• var bit crc_has_error = FALSE
• const byte crc7_table[128] = {
• const byte CRC_ERROR_INVALID_PARAMETER = 1
• var byte crc_error_code = 0
• const byte CRC_ERROR_CALCULATION_FAILED = 2
• const bit CRC_USE_CONSTANT_TABLES = TRUE
• const word CRC16_POLYNOMIAL = 0x1021
• const byte CRC_ERROR_OVERFLOW = 5
• const word crc16_table[256] = {
• const bit CRC_USE_LOOKUP_TABLES = TRUE
• const byte CRC_ERROR_TABLE_NOT_INITIALIZED = 4
• const byte CRC7_POLYNOMIAL = 0x09

Procedures

• crc_print_error(volatile byte out device)
• crc_init()
• crc_set_error(byte in error_code)
• crc_test()
• crc_clear_error()

Functions

• crc_get_error() return byte
• crc7_sd_command(byte in cmd, dword in arg) return byte
• crc7_sd_calculate_bitwise(byte in data[], byte in length) return byte
• crc7_sd_verify(byte in data[], byte in length) return bit
• crc_has_error_status() return bit
• crc16_sd_verify(byte in data[], word in length, word in received_crc) return bit
• crc16_sd_calculate_bitwise(byte in data[], word in length) return word
• crc16_sd_calculate_byte(word in current_crc, byte in data) return word
• crc7_sd_cmd8() return byte
• crc7_sd_calculate(byte in data[], byte in length) return byte
• crc16_sd_calculate(byte in data[], word in length) return word
• crc7_sd_cmd0() return byte

API details

Global variables/contants

• const byte CRC_ERROR_VERIFICATION_FAILED = 3

  No documentation found

• const byte CRC_ERROR_NONE = 0

  CRC error codes
  

• var bit crc_has_error = FALSE

  CRC error handling
  

• const byte crc7_table[128] = {

  CRC7 constant lookup table (stored in program memory)
  

• const byte CRC_ERROR_INVALID_PARAMETER = 1

  No documentation found

• var byte crc_error_code = 0

  No documentation found

• const byte CRC_ERROR_CALCULATION_FAILED = 2

  No documentation found

• const bit CRC_USE_CONSTANT_TABLES = TRUE

  No documentation found

• const word CRC16_POLYNOMIAL = 0x1021

  CRC16 polynomial: x^16 + x^12 + x^5 + 1 (0x1021) - SD card standard
  

• const byte CRC_ERROR_OVERFLOW = 5

  No documentation found

• const word crc16_table[256] = {

  CRC16 constant lookup table (stored in program memory)
  

• const bit CRC_USE_LOOKUP_TABLES = TRUE

  Memory-constrained mode: use constant lookup tables stored in program memory
  This saves RAM by storing tables in Flash memory instead of data memory
  

• const byte CRC_ERROR_TABLE_NOT_INITIALIZED = 4

  No documentation found

• const byte CRC7_POLYNOMIAL = 0x09

  CRC7 polynomial: x^7 + x^3 + 1 (0x09) - SD card standard
  

Procedures

• crc_print_error(volatile byte out device)

  Print CRC error message
  
  

• crc_init()

  Initialize CRC lookup tables for faster calculation
  
  

• crc_set_error(byte in error_code)

  Set CRC error
  
  

• crc_test()

  Test CRC functions with known test vectors
  This procedure can be used for debugging and verification
  
  

• crc_clear_error()

  Clear CRC error
  
  

Functions

• crc_get_error() return byte

  Get CRC error status
  
  

• crc7_sd_command(byte in cmd, dword in arg) return byte

  Calculate CRC7 for a single command frame (6 bytes: command + argument + crc)
  Input: command byte, 32-bit argument
  Output: 7-bit CRC value
  
  

• crc7_sd_calculate_bitwise(byte in data[], byte in length) return byte

  Calculate CRC7 for SD card command frames (bit-by-bit method)
  Input: data array and length
  Output: 7-bit CRC value
  
  

• crc7_sd_verify(byte in data[], byte in length) return bit

  Verify CRC7 for a received command response
  Input: response data array and length
  Output: TRUE if CRC is valid, FALSE otherwise
  
  

• crc_has_error_status() return bit

  Check if CRC has error
  
  

• crc16_sd_verify(byte in data[], word in length, word in received_crc) return bit

  Verify CRC16 for a received data block
  Input: data array, length, and received CRC
  Output: TRUE if CRC is valid, FALSE otherwise
  
  

• crc16_sd_calculate_bitwise(byte in data[], word in length) return word

  Calculate CRC16 for SD card data blocks (bit-by-bit method)
  Input: data array and length
  Output: 16-bit CRC value
  
  

• crc16_sd_calculate_byte(word in current_crc, byte in data) return word

  Calculate CRC16 for a single byte (for incremental calculation)
  Input: current CRC value and new byte
  Output: updated CRC value
  
  

• crc7_sd_cmd8() return byte

  Calculate CRC7 for CMD8 (SEND_IF_COND) command
  CMD8 has a special CRC value of 0x87
  
  

• crc7_sd_calculate(byte in data[], byte in length) return byte

  Calculate CRC7 for SD card command frames
  Input: data array and length
  Output: 7-bit CRC value
  
  

• crc16_sd_calculate(byte in data[], word in length) return word

  Calculate CRC16 for SD card data blocks
  Input: data array and length
  Output: 16-bit CRC value
  
  

• crc7_sd_cmd0() return byte

  Calculate CRC7 for CMD0 (GO_IDLE_STATE) command
  CMD0 has a special CRC value of 0x95
  
  

Related samples

Here are the list of samples which use this library:

18f67j50

18f67j50_sd_card_crc_test.jal