_PROTECTED_WRITE (3)

NAME

avr_io

SYNOPSIS

Macros

#define _PROTECTED_WRITE(reg, value)

#define _PROTECTED_WRITE_SPM(reg, value)

Detailed Description

#include <avr/io.h> 

This header file includes the apropriate IO definitions for the device that has been specified by the -mmcu= compiler command-line switch. This is done by diverting to the appropriate file <avr/ioXXXX.h> which should never be included directly. Some register names common to all AVR devices are defined directly within <avr/common.h>, which is included in <avr/io.h>, but most of the details come from the respective include file.

Note that this file always includes the following files:

#include <avr/sfr_defs.h>
#include <avr/portpins.h>
#include <avr/common.h>
#include <avr/version.h>

 See <avr/sfr_defs.h>: Special function registers for more details about that header file.

Included are definitions of the IO register set and their respective bit values as specified in the Atmel documentation. Note that inconsistencies in naming conventions, so even identical functions sometimes get different names on different devices.

Also included are the specific names useable for interrupt function definitions as documented here.

Finally, the following macros are defined:

*

RAMEND

 The last on-chip RAM address. 

*

XRAMEND

 The last possible RAM location that is addressable. This is equal to RAMEND for devices that do not allow for external RAM. For devices that allow external RAM, this will be larger than RAMEND. 

*

E2END

 The last EEPROM address. 

*

FLASHEND

 The last byte address in the Flash program space. 

*

SPM_PAGESIZE

 For devices with bootloader support, the flash pagesize (in bytes) to be used for the SPM instruction.

*

E2PAGESIZE

 The size of the EEPROM page. 

Macro Definition Documentation

#define _PROTECTED_WRITE(reg, value)

Write value value to IO register reg that is protected through the Xmega configuration change protection (CCP) mechanism. This implements the timed sequence that is required for CCP.

Example to modify the CPU clock:

#include <avr/io.h>

_PROTECTED_WRITE(CLK_PSCTRL, CLK_PSADIV0_bm);
_PROTECTED_WRITE(CLK_CTRL, CLK_SCLKSEL0_bm);

 

#define _PROTECTED_WRITE_SPM(reg, value)

Write value value to register reg that is protected through the Xmega configuration change protection (CCP) key for self programming (SPM). This implements the timed sequence that is required for CCP.

Example to modify the CPU clock:

#include <avr/io.h>

_PROTECTED_WRITE_SPM(NVMCTRL_CTRLA, NVMCTRL_CMD_PAGEERASEWRITE_gc);

 

Author

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