In the SigmaStudio help file, some of the algorithms have input and outputs specified as integer or decimal. Also, in the SigmaDSP datasheets, there are references to 28.0 and 5.23. Also, in SigmaStudio, sometimes cells will have other formats like 5.19. What does this mean?
The value of the top 4 bits will be ignored. Only the 28 LSBs matter. So, you can write 0x0FFFFFFF or 0xFFFFFFFF to the control port, and the DSP will regard them as the same number.