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diff --git a/doc/README.nand b/doc/README.nand new file mode 100644 index 0000000..af7fbfd --- /dev/null +++ b/doc/README.nand @@ -0,0 +1,176 @@ +NAND FLASH commands and notes + +# (C) Copyright 2003 +# Dave Ellis, SIXNET, dge@sixnetio.com +# +# See file CREDITS for list of people who contributed to this +# project. +# +# This program is free software; you can redistribute it and/or +# modify it under the terms of the GNU General Public License as +# published by the Free Software Foundation; either version 2 of +# the License, or (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program; if not, write to the Free Software +# Foundation, Inc., 59 Temple Place, Suite 330, Boston, +# MA 02111-1307 USA + +Commands: + + nand bad + Print a list of all of the bad blocks in the current device. + + nand device + Print information about the current NAND device. + + nand device num + Make device `num' the current device and print information about it. + + nand erase off size + nand erase clean [off size] + Erase `size' bytes starting at offset `off'. Only complete erase + blocks can be erased. + + If `clean' is specified, a JFFS2-style clean marker is written to + each block after it is erased. If `clean' is specified without an + offset or size, the entire flash is erased. + + This command will not erase blocks that are marked bad. There is + a debug option in cmd_nand.c to allow bad blocks to be erased. + Please read the warning there before using it, as blocks marked + bad by the manufacturer must _NEVER_ be erased. + + nand info + Print information about all of the NAND devices found. + + nand read addr ofs size + Read `size' bytes from `ofs' in NAND flash to `addr'. If a page + cannot be read because it is marked bad or an uncorrectable data + error is found the command stops with an error. + + nand read.jffs2 addr ofs size + Like `read', but the data for blocks that are marked bad is read as + 0xff. This gives a readable JFFS2 image that can be processed by + the JFFS2 commands such as ls and fsload. + + nand read.oob addr ofs size + Read `size' bytes from the out-of-band data area corresponding to + `ofs' in NAND flash to `addr'. This is limited to the 16 bytes of + data for one 512-byte page or 2 256-byte pages. There is no check + for bad blocks or ECC errors. + + nand write addr ofs size + Write `size' bytes from `addr' to `ofs' in NAND flash. If a page + cannot be written because it is marked bad or the write fails the + command stops with an error. + + nand write.jffs2 addr ofs size + Like `write', but blocks that are marked bad are skipped and the + is written to the next block instead. This allows writing writing + a JFFS2 image, as long as the image is short enough to fit even + after skipping the bad blocks. Compact images, such as those + produced by mkfs.jffs2 should work well, but loading an image copied + from another flash is going to be trouble if there are any bad blocks. + + nand write.oob addr ofs size + Write `size' bytes from `addr' to the out-of-band data area + corresponding to `ofs' in NAND flash. This is limited to the 16 bytes + of data for one 512-byte page or 2 256-byte pages. There is no check + for bad blocks. + +Configuration Options: + + CFG_CMD_NAND + A good one to add to CONFIG_COMMANDS since it enables NAND support. + + CONFIG_MTD_NAND_ECC_JFFS2 + Define this if you want the Error Correction Code information in + the out-of-band data to be formatted to match the JFFS2 file system. + CONFIG_MTD_NAND_ECC_YAFFS would be another useful choice for + someone to implement. + + CFG_MAX_NAND_DEVICE + The maximum number of NAND devices you want to support. + +NAND Interface: + + #define NAND_WAIT_READY(nand) + Wait until the NAND flash is ready. Typically this would be a + loop waiting for the READY/BUSY line from the flash to indicate it + it is ready. + + #define WRITE_NAND_COMMAND(d, adr) + Write the command byte `d' to the flash at `adr' with the + CLE (command latch enable) line true. If your board uses writes to + different addresses to control CLE and ALE, you can modify `adr' + to be the appropriate address here. If your board uses I/O registers + to control them, it is probably better to let NAND_CTL_SETCLE() + and company do it. + + #define WRITE_NAND_ADDRESS(d, adr) + Write the address byte `d' to the flash at `adr' with the + ALE (address latch enable) line true. If your board uses writes to + different addresses to control CLE and ALE, you can modify `adr' + to be the appropriate address here. If your board uses I/O registers + to control them, it is probably better to let NAND_CTL_SETALE() + and company do it. + + #define WRITE_NAND(d, adr) + Write the data byte `d' to the flash at `adr' with the + ALE and CLE lines false. If your board uses writes to + different addresses to control CLE and ALE, you can modify `adr' + to be the appropriate address here. If your board uses I/O registers + to control them, it is probably better to let NAND_CTL_CLRALE() + and company do it. + + #define READ_NAND(adr) + Read a data byte from the flash at `adr' with the + ALE and CLE lines false. If your board uses reads from + different addresses to control CLE and ALE, you can modify `adr' + to be the appropriate address here. If your board uses I/O registers + to control them, it is probably better to let NAND_CTL_CLRALE() + and company do it. + + #define NAND_DISABLE_CE(nand) + Set CE (Chip Enable) low to enable the NAND flash. + + #define NAND_ENABLE_CE(nand) + Set CE (Chip Enable) high to disable the NAND flash. + + #define NAND_CTL_CLRALE(nandptr) + Set ALE (address latch enable) low. If ALE control is handled by + WRITE_NAND_ADDRESS() this can be empty. + + #define NAND_CTL_SETALE(nandptr) + Set ALE (address latch enable) high. If ALE control is handled by + WRITE_NAND_ADDRESS() this can be empty. + + #define NAND_CTL_CLRCLE(nandptr) + Set CLE (command latch enable) low. If CLE control is handled by + WRITE_NAND_ADDRESS() this can be empty. + + #define NAND_CTL_SETCLE(nandptr) + Set CLE (command latch enable) high. If CLE control is handled by + WRITE_NAND_ADDRESS() this can be empty. + +More Definitions: + + These definitions are needed in the board configuration for now, but + may really belong in a header file. + TODO: Figure which ones are truly configuration settings and rename + them to CFG_NAND_... and move the rest somewhere appropriate. + + #define SECTORSIZE 512 + #define ADDR_COLUMN 1 + #define ADDR_PAGE 2 + #define ADDR_COLUMN_PAGE 3 + #define NAND_ChipID_UNKNOWN 0x00 + #define NAND_MAX_FLOORS 1 + #define NAND_MAX_CHIPS 1 + |