Butterfly network on load data return
A method is shown that is operable to transform and align a plurality of fields from an input to an output data stream using a multilayer butterfly or inverse butterfly network. Many transformations are possible with such a network which may include separate control of each multiplexer. This invention supports a limited set of multiplexer control signals, which enables a similarly limited set of data transformations. This limited capability is offset by the reduced complexity of the multiplexor control circuits.
1. A method of data transformation of an input data word of 2 N sections, where N is an integer, comprising the steps of:
supplying said input data word to a set of N sequential layers of 2 to 1 multiplexers disposed from an input layer to an output layer, wherein: each multiplexer has a first input receiving data of a first corresponding multiplexer of a prior layer, a second input receiving data of a second different corresponding multiplexer of the prior layer, a control input and an output, each multiplexer providing an output corresponding to a selected one of said first input or said second input dependent upon a signal at said control input, each of the N sequential layers including 2 N 2 to 1 multiplexers;
supplying a same control signal to each control input of each multiplexer of a layer; and
outputting transformed data from said outputs of said multiplexers of said output layer.
2. The method of claim 1 wherein:
said step of supplying a same control signal to each control input of each multiplexer of a layer comprises the steps of:
precalculating an N bit shuffle pattern,
precalculating an N bit replicate pattern,
precalculating an N bit rotate pattern, and
supplying to said control input of each multiplexer of a layer a selected one of 1) a corresponding bit of said precalculated shuffle pattern, 2) a corresponding bit of said precalculated replicate pattern, 3) a corresponding bit of said rotate pattern, 4) an exclusive OR of said corresponding bit of said precalculated shuffle pattern and said corresponding bit of precalculated replicate pattern, 5) an exclusive OR of said corresponding bit of said precalculated shuffle pattern and said corresponding bit of precalculated rotate pattern, and 6) an exclusive OR of said corresponding bit of said precalculated replicate pattern and said corresponding bit of precalculated rotate pattern.
3. The method of claim 1 , wherein:
said input data word consists of 64 sections; and
said N sequential layers consists of 6 layers.
4. The method of claim 1 , wherein:
said input data word consists of 64 sections of 8 bits each section; and
said first input, said second input and said output of each of said 2 to 1 multiplixers consists of 8 bits.
5. The method of claim 1 , wherein:
said set of N sequential layers of 2 to 1 multiplexers form a butterfly network.
6. The method of claim 1 , wherein:
said set of N sequential layers of 2 to 1 multiplexers form an inverse butterfly network.