If I recall correctly, somebody on this forum had started a similar thread, and had actually come up with a working FFT implementation on 8051. Put a search and you'll find it. I think he also talked a bit about the performance of the system. You could e-mail him for guidance.

As for DSP applications, I am not sure if the 8051 is the best choice. Look for some DSP IC, or at least microcontrollers with the MAC (Multiply+Accumulate) instruction, as that is a very frequent operation in DSP applications. I guess its mostly the DSPs that have the useful MAC opcode. For DSP uCs look up the TMS and ADSP series ( I can't say how cost effective they would be though)

BTW, how many point FFT are you talking about? If its a very large number, implementing it on 8051 would prove to be unfeasible in a real-time scenario. There was another posting which discussed a parallel multi-processor 8051 solution to overcome the speed problem.

There have ben several other posts on the use of 8051 for FFT and other DSP algorithms...use a search and you'll find a lot of information.

kundi