Atmel CAVR-4 Manual De Usuario

CAVR-4

Descriptions of extended keywords

Reference Guide

_ _version_1

The 

_ _version_1

 keyword is available for backward compatibility. It makes a 

function use the calling convention of the A90 IAR C Compiler instead of the default 
calling convention, both which are described in Calling convention, page 99.

This calling convention is preferred when calling assembler functions from C.S