Re: who may tell me what is the diffence between dsp and fpg
DSP are specialized to do mathematical or physical operations, like FFT, analog signal processing like FSK, QPSK, ... They contain multipliers and specialized hardware.
FPGA are more general. Newer FPGA start having hardware multiplier, so some basic DSP functions can be implemented.
FPGA are mostly used for digital appllications, while DSP are often more used for handling complex analog signals (radar, modems, clock synchronization, sound processing, ...).
DSP are usually much smaller than FPGA, but target specific applications that a much larger FPGA can't handle efficiently. However, you can't implement large digital cores in DSP.
You can use both DSP and FPGA in a project, doing powerfull mathematical operations in the DSP, while using the FPGA for complex digital design.