At reset, the ROM is mapped over the Flash memory so that the ROM boot sequence is always
executed. The boot sequence executed from ROM is as follows:
1. The BA bit (below) is cleared such that ROM is mapped to 0x01xx.xxxx and Flash memory is
mapped to address 0x0.
2. The BOOTCFG register is read. If the EN bit is clear, the status of the specified GPIO pin is
compared with the specified polarity. If the status matches the specified polarity, the ROM is
mapped to address 0x0000.0000 and execution continues out of the ROM Boot Loader.
3. If the status doesn't match the specified polarity, the data at address 0x0000.0004 is read, and
if the data at this address is 0xFFFF.FFFF, the ROM is mapped to address 0x0000.0000 and
execution continues out of the ROM Boot Loader.
4. If there is data at address 0x0000.0004 that is not 0xFFFF.FFFF, the stack pointer (SP) is loaded
from Flash memory at address 0x0000.0000 and the program counter (PC) is loaded from
address 0x0000.0004. The user application begins executing.
The boot loader uses a simple packet interface to provide synchronous communication with the
device. The speed of the boot loader is determined by the internal oscillator (PIOSC) frequency as
it does not enable the PLL. The following serial interfaces can be used:
■ UART0
■ SSI0
■ I
2
C0
■ Ethernet
For simplicity, both the data format and communication protocol are identical for all serial interfaces.
See the Stellaris® Boot Loader User's Guide for information on the boot loader software.
7.2.2.2 Stellaris Peripheral Driver Library
The Stellaris Peripheral Driver Library contains a file called driverlib/rom.h that assists with
calling the peripheral driver library functions in the ROM. The detailed description of each function
is available in the Stellaris® ROM User’s Guide. See the "Using the ROM" chapter of the Stellaris®
Peripheral Driver Library User's Guide for more details on calling the ROM functions and using
driverlib/rom.h.
A table at the beginning of the ROM points to the entry points for the APIs that are provided in the
ROM. Accessing the API through these tables provides scalability; while the API locations may
change in future versions of the ROM, the API tables will not. The tables are split into two levels;
the main table contains one pointer per peripheral which points to a secondary table that contains
one pointer per API that is associated with that peripheral. The main table is located at 0x0100.0010,
right after the Cortex-M3 vector table in the ROM.
DriverLib functions are described in detail in the Stellaris® Peripheral Driver Library User's Guide.
Additional APIs are available for graphics and USB functions, but are not preloaded into ROM. The
Stellaris Graphics Library provides a set of graphics primitives and a widget set for creating graphical
user interfaces on Stellaris microcontroller-based boards that have a graphical display (for more
information, see the Stellaris® Graphics Library User's Guide).
305July 24, 2012
Texas Instruments-Production Data
Stellaris
®
LM3S6G65 Microcontroller
OBSOLETE: TI has discontinued production of this device.
