Public Version
www.ti.com
General-Purpose Memory Controller
Table 10-24. Supported Memory Interfaces (continued)
16-Bit Address/Data Muxed
Function
OneNAND
16-bit NAND
8-bit NAND
pSRAM or NOR Flash
(1)
GPMC_ncs3
nCS3
nCE3
GPMC_ncs4
nCS4
nCE4
GPMC_ncs5
nCS5
nCE5
GPMC_ncs6
nCS6
nCE6
GPMC_ncs7
nCS7
nCE7
gpmc_nadv_ale
nADV (address valid)
ALE (address latch enable)
gpmc_noe
nOE (output enable)
nRE (read enable)
gpmc_nwe
nWE (write enable)
nWE (write enable)
gpmc_nbe0_cle
nBE0 (byte enable)
CLE (command latch enable)
gpmc_nbe1
nBE1
gpmc_nwp
nWP (write protect)
nWP (write protect)
gpmc_wait0
WAIT0
R/nB0 (ready/busy)
gpmc_wait1
WAIT1
R/nB1
gpmc_wait2
WAIT2
R/nB2
gpmc_wait3
WAIT3
R/nB3
10.1.6.2.1.2 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 density by sharing common
areas of the storage transistor, which creates strings of serially connected transistors (in NOR devices,
each transistor stands alone). Because of its high density, NAND is best suited to devices requiring high
capacity data storage, such as pictures, music, or data files. Because of its nonvolatility, NAND is 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 level of the NAND interface signals applied to external devices or memories.
Table 10-25. NAND Interface Bus Operations Summary
Bus operation
CLE
ALE
nCE
nWE
(1)
nRE
(1)
nWP
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
(2)
H
(2)
H
(2)
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
(3)
(1)
RE stands for rising edge, FE stands for falling edge.
(2)
Can be either nCE high, or WE and nRE high
(3)
nWP must be biased to CMOS high or CMOS low for standby.
10.1.6.2.1.3 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 (that is, 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.
2193
SWPU177N – December 2009 – Revised November 2010
Memory Subsystem
Copyright © 2009–2010, Texas Instruments Incorporated