Introduction - If you have any usage issues, please Google them yourself
Two 16-bit integers, the product is always " left growth" , which means the multiplication product of several fixed devices will soon exceed the range of data. And you want to save the 32-bit product into the data memory, it is necessary overhead two machine cycles, and two words of program and RAM unit And, because the multiplier is multiplied by 16, it is difficult in subsequent recursive arithmetic , the product of a multiplier 32-bit input. However, the fractional multiplication, multiplication always " right growth" , which makes the range of data beyond the fixed-point devices are not interested in our part. Under the fractional multiplication, both 32-bit product may be stored, the upper 16 bits can be stored product, which allows to save the results with fewer resources, but also easy for recursive computations. This is why the fixed-point DSP chips are used decimal multiplication causes.