The MSB is the sign of the value and the 23 LSBs are the fractional number. Follows is a list with a few examples of numbers and their corresponding hexadecimal values. How the DSP uses the numbers is very important to know. Believe me, this is a common source of error, that isn't very easy to discover. Back to some fix points.
Multiplications are always two complemental.
Which directly leads us into the construct of the accumulators. In part one, I mentioned that the accumulators could be divided into three registers, A2, A1 and A0. A2, you might wonder, how did that get its value. Simple, doing a multiplication, A2 will be the signextension of the MSB of A1. This sign extension will also occur when a value is move to an accumulator.