Re: Rotating through a four-bit nibble

In lugnet.robotics, Geoffrey Hyde wrote:
> 
> "Jordan Bradford" <[email protected]> wrote in
> message news:[email protected]...
>> In lugnet.robotics, Kevin L. Clague wrote:
>> Why in the world wouldn't the firmware support shifting? The hardware
>> <http://www.delorie.com/gnu/docs/binutils/as_236.html certainly does>.
>> 
>> Heh, using multiply and divide to simulate shifting is kind of backwards.
> 
> The problem is, multiplication and division to a binary CPU, as is the case
> here, is just a whole series of instructions.
> 
> Here is the basic principle explained, partway down the page:
> 
> http://www.evergreen.edu/biophysics/technotes/misc/bin_math.htm
> 
> A link to binary addition and subtraction, from HowStuffWorks article on
> binary (it's actually a framed link to a different site, may have to cut out
> the frame addition if it doesn't work properly), note how it essentially
> works the same as decimal multiplication/division - also partway down the
> page.
> 
> http://computer.howstuffworks.com/framed.htm?parent=bytes.htm&url=http://www.math.grin.edu/~rebelsky/Courses/152/97F/Readings/student-binary.html
> 
> Hope this helps you understand it better!  :)

Understand what better? Binary math? No problems with that!

By "backwards" I meant that multiplication and division by powers of 2 are
usually changed to shift L/R by compilers. Also, I am amused that because the
firmware doesn't use the H8/300's shift instructions for whatever reason, people
are now trying to write software simulations of a trivial hardware operation.