UM0851 datasheet(148/245 Pages) STMICROELECTRONICS

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Non-volatile memory device drivers

UM0851

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Doc ID 16604 Rev 2

Raw mode usage from user space

MTD Utils can be used to access NOR Flash via the MTD layer without a file-system. The

MTD project provides a number of helpful tools for handling NOR Flash.

●

flasherase, flasheraseall: erase and format Flash partitions

●

flashcp: Write filesystem images to NOR Flash

NOR Flash does not have bad blocks so normal busy box commands can also be used to

access it. The random access capability of NOR Flash makes it possible to access any

address of NOR Flash from user mode, once that address is properly mapped.

Raw mode usage from kernel space

NOR Flash can be directly accessed. However, MTD calls such as "mtd->read", "mtd-

>erase" and "mtd->write" can be used to read, erase and write to MTD devices. The

following code snippet shows an example where 4 bytes are read and written in the same

location of the MTD partition number 3.

struct mtd_info *mtd;

int ret = 0;

void *buffer;

size_t retlen = 0;

/* Get MTD info of 3rd partition */

mtd = get_mtd_device(NULL, 3);

if (!mtd) {

err( "Err in get mtd\n");

return;

}

/* Read 4 bytes from partition 3 and store in 'buffer' */

ret = mtd->read(mtd, 0, 4, &retlen, buffer);

if (ret < 0) {

err("Err MTD read=%d\n", ret);

return;

}

/* Write 4 bytes into the partition 3 from the 'buffer' */

ret = (*(mtd->write)) (mtd, 0, 4, &retlen, buffer);

if (ret < 0) {

err("Err MTD write=%d\n", ret);

return;

}

Logical mode usage from user space

The MTD partition can be mounted using a file-system and then can be used. The NOR

Flash partition is supported by JFFS2 only, so make sure that a valid JFFS2 image is

already present in the partition to avoid getting a lot of JFFS2 errror messages.

# mount -t jffs2 /dev/mtdblock3 /mnt

#cp /tmp/song.mp3

/mnt/

#ls /mnt

Song.mp3

UM0851 Datasheet(PDF) 148 Page - STMicroelectronics

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