Introduction
1 Introduction
The TM4C123GH6PM ROM contains the TivaWare™ Peripheral Driver Library and the TivaWare
Boot Loader. The peripheral driver library can be utilized by applications to reduce their flash
footprint, allowing the flash to be used for other purposes (such as additional features in the appli-
cation). The boot loader is used as an initial program loader (when the flash is empty) as well as
an application-initiated firmware upgrade mechanism (by calling back to the boot loader).
There is a table at the beginning of the ROM that 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-M4 vector table in the ROM.
The following table shows a small portion of the API tables in a graphical form that helps to illustrate
the arrangement of the tables:
ROM_APITABLE (at 0x0100.0010)
[0] = ROM_VERSION
[1] = pointer to ROM_UARTTABLE
[2] = pointer to ROM_SSITABLE
[3] = pointer to ROM_I2CTABLE
[4] = pointer to ROM_GPIOTABLE =⇒ ROM_GPIOTABLE
[5] = pointer to ROM_ADCTABLE [0] = pointer to ROM_GPIOPinWrite
[6] = pointer to ROM_COMPARATORTABLE [1] = pointer to ROM_GPIODirModeSet
[7] = pointer to ROM_FLASHTABLE [2] = pointer to ROM_GPIODirModeGet
... ...
From this, the address of the ROM_GPIOTABLE table is located in the memory location at
0x0100.0020. The address of the ROM_GPIODirModeSet() function is contained at offset 0x4
from that table. In the function documentation, this is represented as:
ROM_APITABLE is an array of pointers located at 0x0100.0010.
ROM_GPIOTABLE is an array of pointers located at ROM_APITABLE[4].
ROM_GPIODirModeSet is a function pointer located at ROM_GPIOTABLE[1].
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 naming conventions for the tables
and APIs that are used in this document match those used in that file.
The following is an example of calling the ROM_GPIODirModeSet() function:
#define TARGET_IS_BLIZZARD_RB1
#include <stdbool.h>
#include <stdint.h>
#include "inc/hw_memmap.h"
#include "driverlib/gpio.h"
#include "driverlib/rom.h"
int
main(void)
{
// ...
April 8, 2013 5
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