參數(shù)資料
型號(hào)： NAND512W4B2BN6T
廠商： STMICROELECTRONICS
元件分類(lèi)： PROM
英文描述： 32M X 16 FLASH 3V PROM, 25000 ns, PDSO48
封裝： 12 X 20 MM, PLASTIC, TSOP-48
文件頁(yè)數(shù)： 30/58頁(yè)
文件大?。?/td> 943K
代理商： NAND512W4B2BN6T
NAND512-B, NAND01G-B, NAND02G-B, NAND04G-B, NAND08G-B
36/58
Figure 22. Garbage Collection
Garbage Collection
When a data page needs to be modified, it is faster
to write to the first available page, and the previous
page is marked as invalid. After several updates it
is necessary to remove invalid pages to free some
memory space.
To free this memory space and allow further pro-
gram operations it is recommended to implement
a Garbage Collection algorithm. In a Garbage Col-
lection software the valid pages are copied into a
free area and the block containing the invalid pag-
es is erased (see Figure 22.).
Wear-leveling Algorithm
For write-intensive applications, it is recommend-
ed to implement a Wear-leveling Algorithm to
monitor and spread the number of write cycles per
block.
In memories that do not use a Wear-Leveling Al-
gorithm not all blocks get used at the same rate.
Blocks with long-lived data do not endure as many
write cycles as the blocks with frequently-changed
data.
The Wear-leveling Algorithm ensures that equal
use is made of all the available write cycles for
each block. There are two wear-leveling levels:
■
First Level Wear-leveling, new data is
programmed to the free blocks that have had
the fewest write cycles
■
Second Level Wear-leveling, long-lived data is
copied to another block so that the original
block can be used for more frequently-
changed data.
The Second Level Wear-leveling is triggered when
the difference between the maximum and the min-
imum number of write cycles per block reaches a
specific threshold.
Error Correction Code
An Error Correction Code (ECC) can be imple-
mented in the Nand Flash memories to identify
and correct errors in the data.
For every 2048 bits in the device it is recommend-
ed to implement 22 bits of ECC (16 bits for line par-
ity plus 6 bits for column parity).
An ECC model is available in VHDL or Verilog.
Contact the nearest ST Microelectronics sales of-
fice for more details.
Figure 23. Error Detection
Valid
Page
Invalid
Page
Free
Page
(Erased)
Old Area
AI07599B
New Area (After GC)
New ECC generated
during read
XOR previous ECC
with new ECC
All results
= zero?
22 bit data = 0
YES
11 bit data = 1
NO
1 bit data = 1
Correctable
Error
ECC Error
No Error
ai08332
>1 bit
= zero?
YES
NO
相關(guān)PDF資料
PDF描述
NAND01GR4B2BV1T 64M X 16 FLASH 1.8V PROM, 25000 ns, PDSO48
NAND01GR4B2CV6T 64M X 16 FLASH 1.8V PROM, 25000 ns, PDSO48
NAND01GR4B2CZA1E 64M X 16 FLASH 1.8V PROM, 25000 ns, PBGA63
NAND01GW3A0BZB1 128M X 8 FLASH 3V PROM, 35 ns, PBGA63
NAND512R4A2CZB6E 32M X 16 FLASH 1.8V PROM, 35 ns, PBGA55
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