Atmel CAVR-4 Manual De Usuario

CAVR-4

Descriptions of extended keywords

Reference Guide

_ _intrinsic

The 

_ _intrinsic

 keyword is reserved for compiler internal use only.

_ _io

Controls the storage of data objects in I/O memory space, alternatively data memory 
space.

The 

_ _io

 memory attribute implies that objects are 

_ _no_init

 and volatile, and allows 

objects to be accessed by use of the special I/O instructions in the AVR microcontroller.

Your application may access the AVR I/O system by using the memory-mapped internal 
special function registers (SFRs). To access the AVR I/O system efficiently, the 

_ _io

 

memory attribute should be included in the code.

_ _monitor

Supports atomic execution of a function.

The __

monitor

 keyword causes interrupts to be disabled during execution of the 

function. This allows atomic operations to be performed, such as operations on 
semaphores that control access to resources by multiple processes. A function declared 
with the 

_ _monitor

 keyword is equivalent to any other function in all other respects. 

This keyword can be specified using the 

#pragma

 

object_attribute

 directive.

Avoid using the 

_ _monitor

 keyword on large functions, since the interrupt will 

otherwise be turned off for too long. 

For additional information, see the intrinsic functions __disable_interrupt, page 238, 
and __enable_interrupt, page 238.

Read more about monitor functions in Monitor functions, page 30.

_ _near

Controls the storage of data objects in data memory space.

The 

_ _near

 memory attribute overrides the default data storage of variables given by 

the selected memory model.

0-0x3F

4 bytes (32 bits)

Pointers not allowed I/O

0x60-0xFF

4 bytes (32 bits)

Pointers not allowed Data

0-0xFFFF

 (64 Kbytes)

65535 bytes

16 bits

Data