NandFlash_Disk.rar_2443 K9F2G08_BSP_k9f2g08.c_nand flash DISK

/*+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE. Copyright (c) 2001 Microsoft Corporation Function: CountNumberOfOnes() Description: Counts the number of bits that are "1" in a byte. Returns: Number of bits that are "1". -------------------------------------------------------------------------------*/ #include <windows.h> UCHAR CountNumberOfOnes(UCHAR num) { UCHAR count = 0; while(num) { num=num&(num-1); count++; } return count; } #define DATA_BUFF_LEN 512 #define ECC_BUFF_LEN 3 // # of bytes in ECC #define NO_DATA_ERROR 0 #define ECC_ERROR 1 #define CORRECTABLE_ERROR 12 // Half of the ECC bits are 1 /*++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Function: ECC_CorrectData() Description: Corrects any errors (if possible) in the specified data. Notes: This implemention uses 3 bytes of ECC info for every 512 bytes of data. Furthermore, a only single-bit error can be corrected for every 512 bytes of data. This code is based on the ECC algorithm publicly available on Samsung's FLASH media website. Returns: Boolean indicating if the data was corrected. -------------------------------------------------------------------------------*/ BOOL ECC_CorrectData(LPBYTE pData, LPBYTE pExistingECC, LPBYTE pNewECC) { DWORD i, numOnes, byteLocation, bitLocation; BYTE xorECC[ECC_BUFF_LEN]; //----- 1. Check the parameters ----- if((pData == NULL) || (pExistingECC == NULL) || (pNewECC == NULL)) { return FALSE; } //----- 2. First, determine if this is a single-bit, correctable, error ----- // NOTE: To answer this question, the two ECC values are XOR'd // together and the total # of 1 bits is counted, which // then tell us if we can correct the erroneous single-bit // transition in the data. for(i=0; i<ECC_BUFF_LEN; i++) { xorECC[i] = pExistingECC[i] ^ pNewECC[i]; } numOnes = 0; for(i=0; i<ECC_BUFF_LEN; i++) { numOnes += CountNumberOfOnes(xorECC[i]); } switch(numOnes) { case NO_DATA_ERROR: // Data doesn't contain an error return TRUE; case ECC_ERROR: // Existing ECC value has gone bad! return FALSE; case CORRECTABLE_ERROR: // Single-bit error break; default: // More than a single-bit error return FALSE; } //----- 3. Compute the location of the single-bit error ----- byteLocation = ( ((xorECC[2]&0x02)<<7) | ((xorECC[1]&0x80)) | ((xorECC[1]&0x20)<<1) | ((xorECC[1]&0x08)<<2) | ((xorECC[1]&0x02)<<3) | ((xorECC[0]&0x80)>>4) | ((xorECC[0]&0x20)>>3) | ((xorECC[0]&0x08)>>2) | ((xorECC[0]&0x02)>>1) ); bitLocation = (((xorECC[2]&0x80)>>5) | ((xorECC[2]&0x20)>>4) | ((xorECC[2]&0x08)>>3) ); //----- 4. Correct the single-bit error (set the bit to its complementary value) ----- if(pData[byteLocation] & (0x01 << bitLocation)) { pData[byteLocation] &= ~(0x01 << bitLocation); // 0->1 error, set bit to 0 }else { pData[byteLocation] |= (0x01 << bitLocation); // 1->0 error, set bit to 1 } return TRUE; }