Samsung KFN8GH6Q4M BootRAM Write Protection Operation, Nand Array Write Protection States

Flex-MuxOneNAND4G(KFM4GH6Q4M-DEBx)
Flex-MuxOneNAND8G(KFN8GH6Q4M-DEBx)
Flex-MuxOneNAND16G(KFKAGH6Q4M-DEBx)	FLASH MEMORY

3.4 Write Protection Operation

The Flex-MuxOneNAND can be write-protected to prevent re-programming or erasure of data.

The areas of write-protection are the BootRAM, and the NAND Flash Array.

3.4.1 BootRAM Write Protection Operation

At system power-up, voltage detector in the device detects the rising edge of Vcc and releases the internal power-up reset signal which trig- gers boot code loading. And the designated size data(1KB) is copied from the first page of the first block in the NAND flash array to the BootRAM.

After the bootcode loading is completed, the BootRAM is always locked to protect the boot code from the accidental write.

3.4.2 NAND Flash Array Write Protection Operation

The device has both hardware and software write protection of the NAND Flash array.

Hardware Write Protection Operation

The hardware write protection operation is implemented by executing a Cold or Warm Reset. On power up, the NAND Flash Array is in its default, locked state. The entire NAND Flash array goes to a locked state after a Cold or Warm Reset.

Software Write Protection Operation

The software write protection operation is implemented by writing a Lock command (002Ah) or a Lock-tight command (002Ch) to command register (F220h).

Lock (002Ah) and Lock-tight (002Ch) commands write protects the block defined in the Start Block Address Register F24Ch.

3.4.3 NAND Array Write Protection States

There are three lock states in the NAND Array: unlocked, locked, and locked-tight. On power up, all blocks in the NAND array go to Locked state. The lock status is maintained for each block in the NAND array. Any changes made to lock status of blocks are lost when Cold/warm reset occurs.

Flex-MuxOneNAND supports 4 commands for changing Write Protection states of the blocks: lock/unlock/lock-tight by one block, and All Block Unlock at once.

All Block Unlock command fails if there are lock-tight blocks in flash.

Write Protection Status

The current block Write Protection status can be read in NAND Flash Write Protection Status Register(F24Eh). There are three bits - US, LS, LTS -, which are not cleared by hot reset and NAND Flash Core Reset. These Write Protection status registers are updated when FBA is set, and when Write Protection command is entered.

The followings summarize locking status.

By default, [2:0] values are 010. For example:

-> If host executes unlock block operation, then [2:0] values turn to 100.

-> If host executes lock-tight block operation, then [2:0] values turn to 001.

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