2005..... microSD: An alternative to conventional flash solutions
http://www.esemagazine.com/index.php?option=com_content&task=view&id=11&Itemid=2
"Multiblock mode takes advantage of the multiple internal block buffers present in all microSD cards. In Multiblock mode, when one block buffer gets full during write, the card gives the host access to the other empty block buffers to fill while programming the first block."
Internal work space.....one of the claims of 5787445
However...
"The NAND architecture used by SanDisk and other card vendors currently has Erase Block sizes of (32) or (64) 512 byte blocks, depending on card capacity. In order to re-write a single 512 byte block, all other blocks belonging to the same Erase Block will be simultaneously erased and need to be rewritten. The microSD card manages this function without the requirement of system drivers unlike raw flash memory."
For the high-lite .... because of e.Digitals ability of non-contiguous writes, they do not erase blocks often. They have the ability to mark segments dead for later erase. When enough dead segments are marked, they erase. If in that erase block any of the data segments are still marked as good, they are moved...and the space is flashed or erased. Through management, it is not erased until enough dead segments are marked. They do not have to reclaim space as often as others do.
Edigitals system can work at whatever the physical read /write ability of the flash is. For the above, they work at Erase Block sizes of (32) or (64) 512 byte blocks(read/write blocks). Everything is shadowed or paged to RAM (see figure 2 of the link)and they map the flash.
Do not get confused with blocks....A flash is a make up of arrays. an array is an erase block. The erase block(array) is physically made up of read /write blocks...in this case 512 bytes each. The array will be 32 or 64.
E.Digital can function independent of the erase blocks(arrays) and variably at whatever the physical read/write block size is, such as half of 512 ....or a 256 byte read/write block.
They can drive the system with a cache sized to just one read /write block without the RAM requirement see fig2.
doni
