Xmega Application Note | |||||
#include "clksys_driver.h"
Go to the source code of this file.
Functions | |
void | CCPWrite (volatile uint8_t *address, uint8_t value) |
CCP write helper function written in assembly. | |
void | CLKSYS_AutoCalibration_Enable (uint8_t clkSource, bool extReference) |
This function enables automatic calibration of the selected internal oscillator. | |
void | CLKSYS_Configuration_Lock (void) |
This function lock the entire clock system configuration. | |
uint8_t | CLKSYS_Disable (uint8_t oscSel) |
This function disables the selected oscillator. | |
uint8_t | CLKSYS_Main_ClockSource_Select (CLK_SCLKSEL_t clockSource) |
This function selects the main system clock source. | |
void | CLKSYS_PLL_Config (OSC_PLLSRC_t clockSource, uint8_t factor) |
This function configures the internal high-frequency PLL. | |
void | CLKSYS_Prescalers_Config (CLK_PSADIV_t PSAfactor, CLK_PSBCDIV_t PSBCfactor) |
This function changes the prescaler configuration. | |
void | CLKSYS_RTC_ClockSource_Enable (CLK_RTCSRC_t clockSource) |
This function selects a Real-Time Counter clock source. | |
void | CLKSYS_XOSC_Config (OSC_FRQRANGE_t freqRange, bool lowPower32kHz, OSC_XOSCSEL_t xoscModeSelection) |
This function configures the external oscillator. | |
void | CLKSYS_XOSC_FailureDetection_Enable (void) |
This function enables the External Oscillator Failure Detection (XOSCFD) feature. |
This file contains the function implementations for the XMEGA Clock System driver.
The driver is not intended for size and/or speed critical code, since most functions are just a few lines of code, and the function call overhead would decrease code performance. The driver is intended for rapid prototyping and documentation purposes for getting started with the XMEGA Clock System.
For size and/or speed critical code, it is recommended to copy the function contents directly into your application instead of making a function call.
Several functions use the following construct: "some_register = ... | (some_parameter ? SOME_BIT_bm : 0) | ..." Although the use of the ternary operator ( if ? then : else ) is discouraged, in some occasions the operator makes it possible to write pretty clean and neat code. In this driver, the construct is used to set or not set a configuration bit based on a boolean input parameter, such as the "some_parameter" in the example above.
Copyright (c) 2008, Atmel Corporation All rights reserved.
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Definition in file clksys_driver.c.
void CCPWrite | ( | volatile uint8_t * | address, | |
uint8_t | value | |||
) |
CCP write helper function written in assembly.
This function is written in assembly because of the timecritial operation of writing to the registers.
address | A pointer to the address to write to. | |
value | The value to put in to the register. |
Definition at line 77 of file clksys_driver.c.
References AVR_ENTER_CRITICAL_REGION, and AVR_LEAVE_CRITICAL_REGION.
Referenced by CLKSYS_Configuration_Lock(), CLKSYS_Main_ClockSource_Select(), CLKSYS_Prescalers_Config(), and CLKSYS_XOSC_FailureDetection_Enable().
00078 { 00079 #ifdef __ICCAVR__ 00080 00081 // Store global interrupt setting in scratch register and disable interrupts. 00082 asm("in R1, 0x3F \n" 00083 "cli" 00084 ); 00085 00086 // Move destination address pointer to Z pointer registers. 00087 asm("movw r30, r16"); 00088 #ifdef RAMPZ 00089 asm("ldi R16, 0 \n" 00090 "out 0x3B, R16" 00091 ); 00092 00093 #endif 00094 asm("ldi r16, 0xD8 \n" 00095 "out 0x34, r16 \n" 00096 #if (__MEMORY_MODEL__ == 1) 00097 "st Z, r17 \n"); 00098 #elif (__MEMORY_MODEL__ == 2) 00099 "st Z, r18 \n"); 00100 #else /* (__MEMORY_MODEL__ == 3) || (__MEMORY_MODEL__ == 5) */ 00101 "st Z, r19 \n"); 00102 #endif /* __MEMORY_MODEL__ */ 00103 00104 // Restore global interrupt setting from scratch register. 00105 asm("out 0x3F, R1"); 00106 00107 #elif defined __GNUC__ 00108 AVR_ENTER_CRITICAL_REGION( ); 00109 volatile uint8_t * tmpAddr = address; 00110 #ifdef RAMPZ 00111 RAMPZ = 0; 00112 #endif 00113 asm volatile( 00114 "movw r30, %0" "\n\t" 00115 "ldi r16, %2" "\n\t" 00116 "out %3, r16" "\n\t" 00117 "st Z, %1" "\n\t" 00118 : 00119 : "r" (tmpAddr), "r" (value), "M" (CCP_IOREG_gc), "i" (&CCP) 00120 : "r16", "r30", "r31" 00121 ); 00122 00123 AVR_LEAVE_CRITICAL_REGION( ); 00124 #endif 00125 }
void CLKSYS_AutoCalibration_Enable | ( | uint8_t | clkSource, | |
bool | extReference | |||
) |
This function enables automatic calibration of the selected internal oscillator.
Either the internal 32kHz RC oscillator or an external 32kHz crystal can be used as a calibration reference. The user must make sure that the selected reference is ready and running.
clkSource | Clock source to calibrate, either OSC_RC2MCREF_bm or OSC_RC32MCREF_bm. | |
extReference | True if external crystal should be used as reference. |
Definition at line 260 of file clksys_driver.c.
00261 { 00262 OSC.DFLLCTRL = ( OSC.DFLLCTRL & ~clkSource ) | 00263 ( extReference ? clkSource : 0 ); 00264 if (clkSource == OSC_RC2MCREF_bm) { 00265 DFLLRC2M.CTRL |= DFLL_ENABLE_bm; 00266 } else if (clkSource == OSC_RC32MCREF_bm) { 00267 DFLLRC32M.CTRL |= DFLL_ENABLE_bm; 00268 } 00269 }
void CLKSYS_Configuration_Lock | ( | void | ) |
This function lock the entire clock system configuration.
This will lock the configuration until the next reset, or until the External Oscillator Failure Detections (XOSCFD) feature detects a failure and switches to internal 2MHz RC oscillator.
Definition at line 292 of file clksys_driver.c.
References CCPWrite().
00293 { 00294 CCPWrite( &CLK.LOCK, CLK_LOCK_bm ); 00295 }
uint8_t CLKSYS_Disable | ( | uint8_t | oscSel | ) |
This function disables the selected oscillator.
This function will disable the selected oscillator if possible. If it is currently used as a main system clock source, hardware will disregard the disable attempt, and this function will return zero. If it fails, change to another main system clock source and try again.
oscSel | Bitmask of selected clock. Can be one of the following OSC_RC2MEN_bm, OSC_RC32MEN_bm, OSC_RC32KEN_bm, OSC_XOSCEN_bm, OSC_PLLEN_bm. |
Definition at line 187 of file clksys_driver.c.
Referenced by main().
00188 { 00189 OSC.CTRL &= ~oscSel; 00190 uint8_t clkEnabled = OSC.CTRL & oscSel; 00191 return clkEnabled; 00192 }
uint8_t CLKSYS_Main_ClockSource_Select | ( | CLK_SCLKSEL_t | clockSource | ) |
This function selects the main system clock source.
Hardware will disregard any attempts to select a clock source that is not enabled or not stable. If the change fails, make sure the source is ready and running and try again.
clockSource | Clock source to use as input for the system clock prescaler block. |
Definition at line 225 of file clksys_driver.c.
References CCPWrite().
Referenced by main().
00226 { 00227 uint8_t clkCtrl = ( CLK.CTRL & ~CLK_SCLKSEL_gm ) | clockSource; 00228 CCPWrite( &CLK.CTRL, clkCtrl ); 00229 clkCtrl = ( CLK.CTRL & clockSource ); 00230 return clkCtrl; 00231 }
void CLKSYS_PLL_Config | ( | OSC_PLLSRC_t | clockSource, | |
uint8_t | factor | |||
) |
This function configures the internal high-frequency PLL.
Configuration of the internal high-frequency PLL to the correct values. It is used to define the input of the PLL and the factor of multiplication of the input clock source.
clockSource | Reference clock source for the PLL, must be above 0.4MHz. | |
factor | PLL multiplication factor, must be from 1 to 31, inclusive. |
Definition at line 167 of file clksys_driver.c.
Referenced by main().
00168 { 00169 factor &= OSC_PLLFAC_gm; 00170 OSC.PLLCTRL = (uint8_t) clockSource | ( factor << OSC_PLLFAC_gp ); 00171 }
void CLKSYS_Prescalers_Config | ( | CLK_PSADIV_t | PSAfactor, | |
CLK_PSBCDIV_t | PSBCfactor | |||
) |
This function changes the prescaler configuration.
Change the configuration of the three system clock prescaler is one single operation. The user must make sure that the main CPU clock does not exceed recommended limits.
PSAfactor | Prescaler A division factor, OFF or 2 to 512 in powers of two. | |
PSBCfactor | Prescaler B and C division factor, in the combination of (1,1), (1,2), (4,1) or (2,2). |
Definition at line 206 of file clksys_driver.c.
References CCPWrite().
Referenced by main().
00208 { 00209 uint8_t PSconfig = (uint8_t) PSAfactor | PSBCfactor; 00210 CCPWrite( &CLK.PSCTRL, PSconfig ); 00211 }
void CLKSYS_RTC_ClockSource_Enable | ( | CLK_RTCSRC_t | clockSource | ) |
This function selects a Real-Time Counter clock source.
Selects the clock source for use by the Real-Time Counter (RTC) and enables clock signal routing to the RTC module.
clockSource | Clock source to use for the RTC. |
Definition at line 241 of file clksys_driver.c.
00242 { 00243 CLK.RTCCTRL = ( CLK.RTCCTRL & ~CLK_RTCSRC_gm ) | 00244 clockSource | 00245 CLK_RTCEN_bm; 00246 }
void CLKSYS_XOSC_Config | ( | OSC_FRQRANGE_t | freqRange, | |
bool | lowPower32kHz, | |||
OSC_XOSCSEL_t | xoscModeSelection | |||
) |
This function configures the external oscillator.
freqRange | Frequency range for high-frequency crystal, does not apply for external clock or 32kHz crystals. | |
lowPower32kHz | True of high-quality watch crystals are used and low-power oscillator is desired. | |
xoscModeSelection | Combined selection of oscillator type (or external clock) and startup times. |
Definition at line 141 of file clksys_driver.c.
Referenced by main().
00144 { 00145 OSC.XOSCCTRL = (uint8_t) freqRange | 00146 ( lowPower32kHz ? OSC_X32KLPM_bm : 0 ) | 00147 xoscModeSelection; 00148 }
void CLKSYS_XOSC_FailureDetection_Enable | ( | void | ) |
This function enables the External Oscillator Failure Detection (XOSCFD) feature.
The feature will stay enabled until next reset. Note that the XOSCFD _will_ issue the XOSCF Non-maskable Interrupt (NMI) regardless of any interrupt priorities and settings. Therefore, make sure that a handler is implemented for the XOSCF NMI when you enable it.
Definition at line 280 of file clksys_driver.c.
References CCPWrite().
00281 { 00282 CCPWrite( &OSC.XOSCFAIL, ( OSC_XOSCFDIF_bm | OSC_XOSCFDEN_bm ) ); 00283 }
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