K9F4008W0A-TCB0, K9F4008W0A-TIB0

FLASH MEMORY

9

Identifying Invalid Block(s)

Invalid Block(s)

Invalid blocks are defined as blocks that contain one or more invalid bits whose reliability is not guaranteed by Samsung. The informa-

tion regarding the invalid block(s) is called as the invalid block information. The invalid block information is written to the 1st or the 2nd

page of the invalid block(s) with 00h data. Devices with invalid block(s) have the same quality level or as devices with all valid blocks

and have the same AC and DC characteristics. An invalid block(s) does not affect the performance of valid block(s) because it is iso-

lated from the bit line and the common source line by a select transistor. The system design must be able to mask out the invalid

block(s) via address mapping. The 1st block, which is placed on 00h block address, is fully guaranteed to be a valid block, does not

require Error Correction.

NAND Flash Technical Notes

All device locations are erased(FFh) except locations where the invalid block information is written prior to shipping. Since the invalid

block information is also erasable in most cases, it is impossible to recover the information once it has been erased. Therefore, the

system must be able to recognize the invalid block(s) based on the original invalid block information and create the invalid block table

via the following suggested flow chart(Figure 1). Any intentional erasure of the original invalid block information is prohibited.

Figure 1. Flow chart to create invalid block table.

Start

Set Block Address = 0

Check "FFh" ?

Increment Block Address

Last Block ?

End

No

Yes

Yes

Create (or update)

No

Invalid Block(s) Table