GP Image Header
Initial Software
a) GP device
non-XIP Memory Booting
Initial Software
b) GP device
Peripheral Booting and XIP Memory Booting
Functional Description
Figure 26-26. Image Formats on GP Devices
a) GP Non-XIP Memory Booting
Used for memories which require shadowing (e.g. MMC). Image must begin with a GP header which
contains information on image size and destination address.
b) GP Peripheral Booting and XIP Memory Booting
When memory device is of XIP type (e.g. NOR) the GP header is not needed and the image can
contain code for direct execution. The same image format is used for peripheral booting (where the
code is transferred to internal RAM).
26.1.9.2 Image Format for GP Device
When the booting memory device is non-XIP (e.g. MMC) the image must contain a small header (referred
to as GP header) with the size of the software to load and the destination address where to store it.
The GP header is not needed when booting from an XIP memory device (e.g. NOR) or in case of
peripheral booting. In this case, the peripheral or memory booting image starts directly with executable
code.
Table 26-39. GP Device Image Format
Field
Non-XIP Device Offset
XIP Device Offset
Size[bytes]
Description
Size
0000h
-
4
Size of the image
Address where to store
Destination
0004h
-
4
the image / code entry
point
Image
0008h
0000h
x
Executable code
Note: The “Destination” address field stands for both:
•
Target address for the image copy from the non-XIP storage to the target XIP location (e.g., internal
RAM or SDRAM)
•
Entry point for image code
In other words the user must take care to locate the code entry point to the target address for image copy.
26.1.10 Code Execution
26.1.10.1 Overview
One of the early steps of the Public ROM Code execution is to search for a boot image from the
requested medium (configured by the SYSBOOT pins) and copy it to RAM if needed. If the device is of
GP type and boot interface is non-XIP then the image is simply copied to the provided destination address
(internal or external RAM) and then executed. If the boot interface is of XIP type then the image copy is
not needed and execution is directly given to the XIP memory.
4150
Initialization
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated