Memory booting
No
CH
present?
Yes
No
Yes
Copy image into a target
RAM
Execute CH
Copy CH
to internal RAM
Device is XIP
type?
“dead loop”
Copying failed
Copying failed
Return fail
Execute image
init-014
Public Version
Device Initialization by ROM Code
www.ti.com
Two main groups of permanent booting devices are distinguished by code shadowing. Code shadowing
means copying a code from a nondirectly addressable memory device (non-XIP) to RAM, where the code
can be executed. Directly addressable memory devices are XIP devices.
is the general memory booting procedure common to all types of booting devices. First, the
CH is copied to internal RAM. It is copied even for XIP booting devices, because the device can
temporarily lose a connection with XIP memory during CH execution. The second step is to shadow the
image, if the booting device is not XIP. The last step is image execution.
Unsuccessful execution or return from image results in a dead loop.
If CH copying or shadowing fails, memory booting returns to the main booting procedure, which selects
the next booting device for booting.
Figure 26-14. Memory Booting Procedure
26.4.7.2 Non-XIP Memory
shows the procedure used when memory booting runs with non-XIP booting devices. The
grayed procedures are specific to each booting device. NAND and OneNAND/Flex-OneNAND booting
devices use up to four copies of the image in the first four physical blocks. Therefore, the ROM code
searches for the image in the first four physical blocks of these booting devices. Other booting devices use
only one copy of the image and the block loop runs only once.
During image shadowing on a GP device, the CH is expected to be in a separate sector before the initial
software.
3542
Initialization
SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated
