CS0
OE
WE
t
OEon
WEon
, t
t
rddata
t
OEoff
WEoff
,
t
t
wr
rd
CEoff
, t , t
Functional Description
•
Only supports devices where Chip Select can be de-asserted during read, program or erase cycles,
without interrupting the operation
•
Device Identification based on ONFI or ROM table
•
ECC correction : 8 bits/sector for most devices (16b/sector for devices with large spare area)
•
Support for disabling ECC correction, so than the in-built ECC correction mechanisms on some
NANDs can be used.
•
GPMC timings adjusted for NAND access
•
GPMC clock is 50MHz
•
Device connected to GPMC_CSN0
•
Wait pin signal GPMC_WAIT0 connected to NAND BUSY output
•
Four physical blocks are searched for an image. The block size depends on device.
26.1.7.4.2 Initialization and Detection
The initialization routine for NAND devices consists in three parts: GPMC initialization, device detection
with parameters determination and finally bad block detection.
ONFI Support
The NAND identification starts with ONFI detection. For more information on ONFI standard, see the
Open NAND Flash Interface Specification (
GPMC Initialization
The GPMC interface is configured as such it can be used for accessing NAND devices. The address bus
is released since a NAND device does not use it. The data bus width is initially set to 16 bits; and changed
to 8 bits if needed after device parameters determination. The following scheme is applied since NAND
devices require different timings when compared to regular NOR devices:
Figure 26-11. GPMC NAND Timings
Table 26-12. NAND Timings Parameters
Parameter
Description
Value [clock cycles]
t
wr
write cycle period
30
t
rd
read cycle period
30
t
CEon
CE low (not marked on the figure)
0
t
OEon
CE low to OE low time
7
t
WEon
CE low to WE low time
5
4119
SPRUH73H – October 2011 – Revised April 2013
Initialization
Copyright © 2011–2013, Texas Instruments Incorporated