This is a general MCU question, and not really addressed to a particular architecture. Say you have an 8-bit MCU that can do 8-bit x 8-bit unsigned integer multiplication, with the result being 16 bits. Would it be possible to use that built-in arithmetic routine to perform a multiplication of M x N bit unsigned integers, where M and N are larger than 8. For instance, would it be possible to perform an 18 x 16 bit unsigned integer multiplication? Not directly of course, but by writing a procedure for it. If so, does anyone have a link to a website describing these algorithms?