Methods and apparatus for providing bit-reversal and multicast functions utilizing DMA controller

Abstract

Techniques for providing improved data distribution to and collection from multiple memories are described. Such memories are often associated with and local to processing elements (PEs) within an array processor. Improved data transfer control within a data processing system provides support for radix 2, 4 and 8 fast Fourier transform (FFT) algorithms through data reordering or bit-reversed addressing across multiple PEs, carried out concurrently with FFT computation on a digital signal processor (DSP) array by a DMA unit. Parallel data distribution and collection through forms of multicast and packet-gather operations are also supported.

1 . A method for permuting data before the data is sent to processing elements (PE) for inbound transfers or before being sent to system memories for outbound transfers comprising the steps of: 
 reordering data within a data element; and    performing other stream oriented operations including masking, data merging or complementing.    
     
     
         2 . The method of  claim 1  wherein said step of data merging further comprises: 
 performing a logical AND operation with a mask followed by performing a logical OR operation with a constant.    
     
     
         3 . The method of  claim 1  wherein said step of complementing further comprises using a logical XOR operation with a specified mask.  
     
     
         4 . A method for performing processing element (PE) packing-gather operations comprising the following steps: 
 setting a packing-gather operations type indicator to indicate that each PE drives data onto a different group of data wires to return to a transfer controller ODQ; and    determining the packing-gather operations type indicator to control PE deriving of data.    
     
     
         5 . The method of  claim 4  wherein a byte size gather over 4 PEs specifies that each PE supplies one byte of a 32-bit word to be returned to the ODQ for return to the system data bus.  
     
     
         6 . A method for performing processing element (PE) relative gather-sum operations comprising: 
 specifying a summary transfer parameter, N, specifying a number of data elements which are to be summed as they are read from local memories;    summing the N elements to form a single data element;    repeating the previous steps; and    transferring a single data element to an ODQ as a sum result for every N elements read from local memories.    
     
     
         7 . The method of  claim 6  further comprising the step of transferring the sum result from the ODQ to a system data bus.  
     
     
         8 . A method for performing processing element (PE) relative unpack-distribute operations comprising the steps of: 
 setting an unpack-distribute operations type indicator to indicate that each PE LMIU receives data from a different group of data wires to be written to its local memory; and    determining the unpack-distribute operations type indicator to control each PE LMIU's receipt of data.