TM4C1231H6PM Datasheet, PDF (492/1146 Pages) Texas Instruments – Tiva™ TM4C1231H6PM Microcontroller

Internal Memory
8.2.2.2
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
■ I²C0
■ USB
The data format and communication protocol are identical for the UART0, SSI0, and I2C0 interfaces.
Note: The Flash-memory-resident version of the boot loader also supports CAN.
See the TivaWare™ Boot Loader for C Series User's Guide (literature number SPMU301) for
information on the boot loader software. The USB boot loader uses the standard Device Firmware
Upgrade USB device class.
Considerations When Using the UART Boot Loader in ROM
U0Tx is not driven by the ROM boot loader until the auto-bauding process has completed. If U0Tx
is floating during this time, the receiver it is connected to may see transitions on the signal, which
could be interpreted by its UART as valid characters. To handle this situation, put a pull-up or
pull-down on U0Tx, providing a defined state for the signal until the ROM boot loader begins driving
U0Tx. A pull-up is preferred as it indicates that the UART is idle, rather than a pull-down, which
indicates a break condition.
TivaWare Peripheral Driver Library
The TivaWare 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 Tiva™ C Series TM4C123x ROM User’s Guide (literature number SPMU367).
See the "Using the ROM" chapter of the TivaWare™ Peripheral Driver Library for C Series User's
Guide (literature number SPMU298) for more details on calling the ROM functions and using
driverlib/rom.h. The driverlib/rom_map.h header file is also provided to aid portability
when using different Tiva™ C Series devices which might have a different subset of DriverLib
functions in ROM. The driverlib/rom_map.h header file uses build-time labels to route function
calls to the ROM if those functions are available on a given device, otherwise, it routes to
Flash-resident versions of the functions.
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-M4F vector table in the ROM.
DriverLib functions are described in detail in the TivaWare™ Peripheral Driver Library for C Series
User's Guide (literature number SPMU298).
Additional APIs are available for graphics and USB functions, but are not preloaded into ROM. The
TivaWare Graphics Library provides a set of graphics primitives and a widget set for creating graphical
user interfaces on Tiva™ C Series microcontroller-based boards that have a graphical display (for
more information, see the TivaWare™ Graphics Library for C Series User's Guide (literature number
SPMU300)).
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June 12, 2014
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