To write in asm:

 - the file must end with .s

 - read the help file on "Calling Convention and Assembler Interface." 
   It tells you which registers you can use and pass between functions

 - read the help file on "Assembler Directives." 
   It tells you which directives are acceptable.

We recommend that you take look at some examples under \iccv7avr\examples.12. Some of them contain asm files. It should give you an idea of the general asm file format.

richard@imagecraft.com