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//*****************************************************************************
//
// bitband.c - Bit-band manipulation example.
//
// Copyright (c) 2012 Texas Instruments Incorporated. All rights reserved.
// Software License Agreement
//
// Texas Instruments (TI) is supplying this software for use solely and
// exclusively on TI's microcontroller products. The software is owned by
// TI and/or its suppliers, and is protected under applicable copyright
// laws. You may not combine this software with "viral" open-source
// software in order to form a larger program.
//
// THIS SOFTWARE IS PROVIDED "AS IS" AND WITH ALL FAULTS.
// NO WARRANTIES, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT
// NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. TI SHALL NOT, UNDER ANY
// CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
// DAMAGES, FOR ANY REASON WHATSOEVER.
//
// This is part of revision 9453 of the EK-LM4F120XL Firmware Package.
//
//*****************************************************************************
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "driverlib/debug.h"
#include "driverlib/gpio.h"
#include "driverlib/fpu.h"
#include "driverlib/pin_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/systick.h"
#include "driverlib/rom.h"
#include "utils/uartstdio.h"
//*****************************************************************************
//
//! \addtogroup example_list
//! <h1>Bit-Banding (bitband)</h1>
//!
//! This example application demonstrates the use of the bit-banding
//! capabilities of the Cortex-M4F microprocessor. All of SRAM and all of the
//! peripherals reside within bit-band regions, meaning that bit-banding
//! operations can be applied to any of them. In this example, a variable in
//! SRAM is set to a particular value one bit at a time using bit-banding
//! operations (it would be more efficient to do a single non-bit-banded write;
//! this simply demonstrates the operation of bit-banding).
//
//*****************************************************************************
//*****************************************************************************
//
// The value that is to be modified via bit-banding.
//
//*****************************************************************************
static volatile unsigned long g_ulValue;
//*****************************************************************************
//
// The error routine that is called if the driver library encounters an error.
//
//*****************************************************************************
#ifdef DEBUG
void
__error__(char *pcFilename, unsigned long ulLine)
{
}
#endif
//*****************************************************************************
//
// Delay for the specified number of seconds. Depending upon the current
// SysTick value, the delay will be between N-1 and N seconds (i.e. N-1 full
// seconds are guaranteed, along with the remainder of the current second).
//
//*****************************************************************************
void
Delay(unsigned long ulSeconds)
{
//
// Loop while there are more seconds to wait.
//
while(ulSeconds--)
{
//
// Wait until the SysTick value is less than 1000.
//
while(ROM_SysTickValueGet() > 1000)
{
}
//
// Wait until the SysTick value is greater than 1000.
//
while(ROM_SysTickValueGet() < 1000)
{
}
}
}
//*****************************************************************************
//
// This example demonstrates the use of bit-banding to set individual bits
// within a word of SRAM.
//
//*****************************************************************************
int
main(void)
{
unsigned long ulErrors, ulIdx;
//
// Enable lazy stacking for interrupt handlers. This allows floating-point
// instructions to be used within interrupt handlers, but at the expense of
// extra stack usage.
//
ROM_FPULazyStackingEnable();
//
// Set the clocking to run directly from the crystal.
//
ROM_SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN |
SYSCTL_XTAL_16MHZ);
//
// Initialize the UART interface.
//
ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
GPIOPinConfigure(GPIO_PA0_U0RX);
GPIOPinConfigure(GPIO_PA1_U0TX);
ROM_GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1);
UARTStdioInit(0);
UARTprintf("\033[2JBit banding...\n");
//
// Set up and enable the SysTick timer. It will be used as a reference
// for delay loops. The SysTick timer period will be set up for one
// second.
//
ROM_SysTickPeriodSet(ROM_SysCtlClockGet());
ROM_SysTickEnable();
//
// Set the value and error count to zero.
//
g_ulValue = 0;
ulErrors = 0;
//
// Print the initial value to the UART.
//
UARTprintf("\r%08x", g_ulValue);
//
// Delay for 1 second.
//
Delay(1);
//
// Set the value to 0xdecafbad using bit band accesses to each individual
// bit.
//
for(ulIdx = 0; ulIdx < 32; ulIdx++)
{
//
// Set this bit.
//
HWREGBITW(&g_ulValue, 31 - ulIdx) = (0xdecafbad >> (31 - ulIdx)) & 1;
//
// Print the current value to the UART.
//
UARTprintf("\r%08x", g_ulValue);
//
// Delay for 1 second.
//
Delay(1);
}
//
// Make sure that the value is 0xdecafbad.
//
if(g_ulValue != 0xdecafbad)
{
ulErrors++;
}
//
// Make sure that the individual bits read back correctly.
//
for(ulIdx = 0; ulIdx < 32; ulIdx++)
{
if(HWREGBITW(&g_ulValue, ulIdx) != ((0xdecafbad >> ulIdx) & 1))
{
ulErrors++;
}
}
//
// Print out the result.
//
if(ulErrors)
{
UARTprintf("\nErrors!\n");
}
else
{
UARTprintf("\nSuccess!\n");
}
//
// Loop forever.
//
while(1)
{
}
}
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