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/*
* Copyright (C) 2014 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup cpu
* @{
*
* @file
* @brief low-power mode implementation for MSP430 MCUs
*
* @author Kévin Roussel <Kevin.Roussel@inria.fr>
* @author Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de>
* @author Thomas Eichinger <thomas.eichinger@fu-berlin.de>
*
* @}
*/
#include <assert.h>
#include <stdio.h>
#if (__GNUC__ >= 4) && (__GNUC_MINOR__ > 5)
#include <intrinsics.h> // MSP430-gcc compiler instrinsics
#endif
#include "board.h"
#include <msp430.h>
#include "lpm.h"
/* Initialise the MSP430 power-saving mechanisms. */
void lpm_init(void)
{
/* nothing to initialize on MSP430s: everything is done by fiddling
with 4 bits of the status register (SR). */
/* just ensure MCU is fully up and running at start */
lpm_awake();
}
/* Change the current power-saving mode. */
enum lpm_mode lpm_set(enum lpm_mode target)
{
enum lpm_mode last_mode = lpm_get();
/* ensure that interrupts are enabled before going to sleep,
or we're bound to hang our MCU! */
assert((target == LPM_ON) || (__read_status_register() & GIE));
switch (target) {
case LPM_ON:
/* fully running MCU */
__bic_status_register(CPUOFF | OSCOFF | SCG0 | SCG1);
break;
case LPM_IDLE:
/* lightest mode => LPM0 mode of MSP430 */
__bic_status_register(OSCOFF | SCG0 | SCG1);
/* only stops CPU block */
__bis_status_register(CPUOFF);
break;
case LPM_SLEEP:
/* mid-level mode => LPM1 mode of MSP430 */
__bic_status_register(OSCOFF | SCG1);
/* stops CPU and master clock blocks */
__bis_status_register(CPUOFF | SCG0);
break;
case LPM_POWERDOWN:
/* deep-level mode => LPM3 mode of MSP430 */
__bic_status_register(OSCOFF);
/* stops all blocks except auxiliary clock (timers) */
__bis_status_register(CPUOFF | SCG0 | SCG1);
break;
case LPM_OFF:
/* MCU totally down (LPM4), only RESET or NMI can resume execution */
__bis_status_register(CPUOFF | OSCOFF | SCG0 | SCG1);
/* all blocks off */
break;
default:
assert(0); /* abort if NDEBUG is not defined */
break;
}
return last_mode;
}
#define LPM_MASK_SR (CPUOFF | OSCOFF | SCG0 | SCG1)
/* Return the current LPM mode of the MSP430 MCU. */
enum lpm_mode lpm_get(void)
{
enum lpm_mode current_mode = LPM_UNKNOWN;
unsigned int current_sr = __read_status_register();
switch (current_sr & LPM_MASK_SR) {
case CPUOFF + OSCOFF + SCG0 + SCG1: /* MSP430's LPM4 */
current_mode = LPM_OFF;
break;
case CPUOFF + SCG0 + SCG1: /* MSP430's LPM3 */
case CPUOFF + SCG1: /* MSP430's LPM2 */
current_mode = LPM_POWERDOWN;
break;
case CPUOFF + SCG0: /* MSP430's LPM1 */
current_mode = LPM_SLEEP;
break;
case CPUOFF: /* MSP430's LPM1 */
current_mode = LPM_IDLE;
break;
case 0: /* MSP430 active */
current_mode = LPM_ON;
break;
}
return current_mode;
}
/* resume the MSP430 MCU */
inline void lpm_awake(void)
{
/* disable all power savings mechanisms */
__bic_status_register(CPUOFF | OSCOFF | SCG0 | SCG1);
}
/* the following two functions have no actual role to play MSP430s */
inline void lpm_begin_awake(void) { }
inline void lpm_end_awake(void) { }
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