unsigned char RETURN;

It's not a good idea to use language keywords for identifiers - even if you have made it uppercase!

Initial_LCD(); // Run function Initial_LCD 
Init_CPU();    // do all initializations 

Comments like "Run function Initial_LCD" by a call to Initial_LCD add no value. The comment should explain why you call the function here.

Do you really want to initialise the LCD before you've run Init_CPU?

//define function convert 
unsigned char convert(unsigned char channel)

Again, this comment adds no value.
A useful function comment would:

State the purpose of the function;

Describe the parameters;

Describe any necessary pre-conditions;

State any global variable usage;

Describe the return value;
etc

http://www.ganssle.com/articles/Comments.htm
http://www.ganssle.com/articles/astyle.htm
http://www.ganssle.com/misc/fsm.doc