The PDSP16515A performs Forward or Inverse Fast Fourier Transforms on complex or real data sets containing up to 1024 points. Data and coefficient input are both represented by 16 bits. Data is expanded internally to 18 bits and subject to Block Floating Point arithmetic to preserve a greater dynamic range. An internal RAM is provided which can hold up to 1024 complex data points. This removes the memory transfer bottleneck, inherent in building block solutions. Its organisation allows the PDSP16515A to simultaneously input new data, transform data stored in the RAM, and to output previous results. No external buffering is needed for transforms containing up to 256 points, and the PDSP16515A can be directly connected to an A/D converter to perform continuous transforms. The user can choose to overlap data blocks by either 0%, 50%, or 75%. Inputs and outputs are synchronous to the 45MHz system clock used for internal operations.