Visible to Intel only — GUID: mwh1416946782123
Ixiasoft
Visible to Intel only — GUID: mwh1416946782123
Ixiasoft
6.10.3. Fine-Grained Flash Access
- alt_get_flash_info()
- alt_erase_flash_block()
- alt_write_flash_block()
By the nature of flash memory, you cannot erase a single address in a block. You must erase (that is, set to all ones) an entire block at a time. Writing to flash memory can only change bits from 1 to 0; to change any bit from 0 to 1, you must erase the entire block along with it.
Therefore, to alter a specific location in a block while leaving the surrounding contents unchanged, you must read out the entire contents of the block to a buffer, alter the value(s) in the buffer, erase the flash block, and finally write the whole block-sized buffer back to flash memory. The fine-grained flash access functions automate this process at the flash block level.
#include <stdio.h> #include <string.h> #include "sys/alt_flash.h" #define BUF_SIZE 1024 int main () { alt_flash_fd* fd; int ret_code; char source[BUF_SIZE]; char dest[BUF_SIZE]; /* Initialize the source buffer to all 0xAA */ memset(source, 0xAA, BUF_SIZE); fd = alt_flash_open_dev("/dev/ext_flash"); if (fd!=NULL) { ret_code = alt_write_flash(fd, 0, source, BUF_SIZE); if (ret_code==0) { ret_code = alt_read_flash(fd, 0, dest, BUF_SIZE); if (ret_code==0) { /* * Success. * At this point, the flash is all 0xAA and we * have read that all back to dest */ } } alt_flash_close_dev(fd); } else { printf("Cannot open flash device\n"); } return 0; }