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Folding 〔K. K. Parhi, C.-Y. Wang, and A. P. Brown, "synthesis of control circuits in folded pipelined DSP architectures," IEEE Journal of Solid State Circuits, vol. 27, no. 1, pp. 29-43, Jan. 1992〕 is a transformation technique using in DSP architecture implementation for minimizing the number of functional blocks in synthesizing DSP architecture. Folding was first developed by Keshab K. Parhi and his students in 1992. Its concept is contrary to unfolding. Folding transforms an operation from a unit-time processing to ''N'' unit-times processing where ''N'' is called folding factor. Therefore, multiple same operations (less than ''N'') used in original system could be replaced with a signal operation block in transformed system. Thus, in ''N'' unit-times, a functional block in transformed system could be reused to perform ''N'' operations in original system. While the folding transformation reduces the number of functional units in the architecture, it needs more memory element to store the temporary data. The reason is that multiple data produced from an operation block needs to be distinguished from ''N'' data produced from original operations. Therefore, the number of register may be increased. Furthermore, it needs additional multiplexer for switching different operation paths. Hence, the number of switching elements would also be increased. To counterattack such issues, the considerations of folding is * How to schedule multiple operations into an operation block. * How to schedule the memory element for reducing the number of registers and multiplexers. ==Example== The following graph shows the example of folding transformation. The original DSP system produces ''y''(''n'') at each unit time. The transformed DSP system produces ''y''(''n'') in each 2 ''l'' where each 2 ''l'' increase 1 ''n'', index of ''y''. The resource used in original system are 2 adders, and the resource used in transformed system are 1 adder, 1 register, 3 multiplexer. The functional block, adder, is therefore reduced. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Folding (DSP implementation)」の詳細全文を読む スポンサード リンク
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