Electronic device with memory erased by page
The invention relates to a method for managing an memory LNVM erasable by block. The method comprises an index management of the memory blocks wherein the index indicates if a block is erased (Erased) or to be erased (TBE). A memory manager performs a block erasing when the memory is not in use and a block is to be erased and when the number of erased blocks is lower than a predetermined number.
1. A method for managing a non-volatile memory erasable by block comprising:
managing an index of the memory blocks wherein the index indicates, in a first field, for each block whether the block is erased and, in a second field, whether the block is no more used and therefore a candidate to be erased, by a memory manager performing a block erasure when the memory is not in use and a block is to be erased and when the number of erased blocks is lower than a predetermined number.
2. The method of claim 1 , wherein the block erasing is made on the oldest available block that is not erased.
3. The method of claim 1 , wherein the index management is made on a number of blocks lower than the total number of blocks of the memory.
4. The method of claim 1 , wherein the memory is inside an electronic device receiving commands according ISO7816 or ISO14443, and wherein the block erasing is made during an idle time of said commands.
5. The method of claim 1 wherein the second field of the index indicating that a block is no more used corresponds to a metadata field for the block indicating that the block is no more used.
6. The method of claim 5 wherein the metadata field for the block indicating that the block is no more used is a word having at least one bit corresponding to each page of a block wherein the at least one bit corresponding to each page is set to binary 0 when the page is no more used whereby if all pages of a block are no more used, the word having at least one bit corresponding to each page of a block has the value zero.
7. The method of claim 1 further comprising:
storing in a metadata field for each block no more used a position for the block in an erasing queue and in the index of the memory blocks; and
when performing block erasure, erasing a block by selecting a block to be erased based on the indicated positions in the erasing queue.
8. The method of claim 1 comprising:
storing a to-be-erased field and a no-more-used field in a metadata area of each block;
storing the index of the memory blocks in a dynamic memory; and
in the event of power off, storing the index in non-volatile memory.
9. The method of claim 1 comprising:
storing a to-be-erased field and a no-more-used field in a metadata area of each block;
storing the index of the memory blocks in a dynamic memory; and
in the event of power on, reconstructing the index from the metadata area of each block.
10. An electronic device comprising at least one electrically erasable non-volatile memory which is erasable by blocks and a memory controller wherein the memory controller comprises an index of the memory storing, in a first field, for each block an indication of whether the block is erased and, in a second field, whether the block is no more used and therefore a candidate to be erased, wherein the memory controller performs a block erasure when the memory is not in use and a block is to be erased and when the index indicates that the number of erased blocks is lower than a predetermined number.
11. The electronic device of claim 10 wherein the second field of the index indicating that a block is no more used corresponds to a metadata field for the block indicating that the block is no more used.
12. The electronic device of claim 11 wherein the metadata field for the block indicating that the block is no more used is a word having at least one bit corresponding to each page of a block wherein the at least one bit corresponding to each page is set to binary 0 when the page is no more used whereby if all pages of a block are no more used, the word having at least one bit corresponding to each page of a block has the value zero.
13. The electronic device of claim 10 further comprising:
an erase-queue-position metadata field stored in each block no more used and in the index of the memory blocks, the erase-queue-position indicating a position for the block in an erasing queue; and
when performing block erasure, erasing a block by selecting a block to be erased based on the indicated positions in the erasing queue.
14. The electronic device of claim 10 comprising:
a to-be-erased field and a no-more-used field in a metadata area of each block;
wherein the index of the memory blocks is stored in a dynamic memory; and
the memory controller is configured to, in the event of power off, storing the index in non-volatile memory.
15. The electronic device of claim 10 comprising:
a to-be-erased field and a no-more-used field in a metadata area of each block;
wherein the index of the memory blocks is stored in a dynamic memory; and
the memory controller is configured to, in the event of power on, reconstructing the index from the metadata area of each block.