Atmel CAVR-4 Manual De Usuario

CAVR-4

Descriptions of intrinsic functions

Reference Guide

_ _multiply_unsigned

unsigned int _ _multiply_unsigned(unsigned char, unsigned char);

Generates a 

MUL

 instruction.

_ _no_operation

void _ _no_operation(void);

Generates a 

NOP

 instruction.

_ _require

void _ _require(void *);

Sets a constant literal as required. 

One of the prominent features of the IAR XLINK Linker is its ability to strip away 
anything that is not needed. This is a very good feature because it reduces the resulting 
code size to a minimum. However, in some situations you may want to be able to 
explicitly include a piece of code or a variable even though it is not directly used.

The argument to 

_ _require

 could be a variable, a function name, or an exported 

assembler label. It must, however, be a constant literal. The label referred to will be 
treated as if it would be used at the location of the 

_ _require

 call.

In the following example, the copyright message will be included in the generated 
binary file even though it is not directly used. 

#include <intrinsics.h>

char copyright[] = "Copyright 2005 by XXXX";

void main(void)

{

_ _require(copyright);

[... the rest of the program ...]

}

_ _restore_interrupt

void _ _restore_interrupt(unsigned char oldState);

This intrinsic function will restore the interrupt flag to the specified state.

Note: The value of 

 must be the result of a call to the 

_ _save_interrupt

 

intrinsic function.

_ _reverse

unsigned int _ _reverse(unsigned int);

This intrinsic function reverses the byte order of the value given as parameter. Avoid 
using 

_ _reverse

 in complex expressions as it might introduce extra register copying.