Preliminary
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Use Cases And Tips
5.4.2.3
NAND Interface Protocol
NAND flash architecture, introduced in 1989, is a flash technology. NAND is a page-oriented memory
device, that is, read and write accesses are done by pages. NAND achieves great density by sharing
common areas of the storage transistor, which creates strings of serially connected transistors (in NOR
devices, each transistor stands alone). Thanks to its high density NAND is best suited to devices
requiring high capacity data storage, such as pictures, music, or data files. NAND non-volatility, makes
of it a good storage solution for many applications where mobility, low power, and speed are key
factors. Low pin count and simple interface are other advantages of NAND.
summarizes the NAND interface signals level applied to external device or memories.
Table 5-53. NAND Interface Bus Operations Summary
Bus Operation
CLE
ALE
CE
WE
RE
WP
Read (cmd input)
H
L
L
RE
H
x
Read (add input)
L
H
L
RE
H
x
Write (cmd input)
H
L
L
RE
H
H
Write (add input)
L
H
L
RE
H
H
Data input
L
L
L
RE
H
H
Data output
L
L
L
H
FE
x
Busy (during read)
x
x
H
H
H
x
Busy (during program)
x
x
x
x
x
H
Busy (during erase)
x
x
x
x
x
H
Write protect
x
x
x
x
x
L
Stand-by
x
x
H
x
x
H/L
5.4.2.4
NOR Interface Protocol
NOR flash architecture, introduced in 1988, is a flash technology. Unlike NAND, which is a sequential
access device, NOR is directly addressable; i.e., it is designed to be a random access device. NOR is
best suited to devices used to store and run code or firmware, usually in small capacities. While NOR
has fast read capabilities it has slow write and erase functions compared to NAND architecture.
summarizes the NOR interface signals level applied to external device or memories.
Table 5-54. NOR Interface Bus Operations Summary
Bus Operation
CLK
ADV
CS
OE
WE
WAIT
DQ[15:0]
Read (asynchronous)
x
L
L
L
H
Asserted
Output
Read (synchronous)
Running
L
L
L
H
Driven
Output
Read (burst suspend)
Halted
x
L
H
H
Active
Output
Write
x
L
L
H
L
Asserted
Input
Output disable
x
x
L
H
H
Asserted
High-Z
Standby
x
x
H
x
x
High-Z
High-Z
661
SPRUGX9 – 15 April 2011
General-Purpose Memory Controller (GPMC)
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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