| With the development of micro-electronics and computer architecture,64 bit computing has become the mainstream in the development of microprocessors.Barrel Shifter is integrated in all kinds of microprocessor and can process Shift-Instructions or Shift-Microoperations.Nowadays,the technology of shifter design has become comparatively mature,and there are many kinds of structures in implementing a shifter. Designers should select the right structure according to given functions.Generally, shifters with a single function have simple structures,and shifters with multiple functions have complex structures.This paper presentsa design of 64-bit Multi-Mode Barrel Shifter.This shifter can carry out shift instructions or micro-operations in 64-bit SISD mode and in SIMD mode (including 16×4 mode and 32×2 mode),such as Logical-Shift,Arithmetic-Shift and rotate,and it can also generate zero-flag and overflow-flag.First of all,this paper summarizes four kinds of structures according to the function requirement,such as MUX-based data-reversal barrel shifter,mask-based data-reversal barrel shifter,mask-based two's complement barrel shifter and mask-based one's complement barrel shifter.Then in the course of this paper's design,a semi-custom design is first adopted.In this way we can make a compare of different structures.It is proved that the mask-based data-reversal barrel shifter is the best structure in the four structures.The result of synthesis delay is 1.30ns and it is 1.679ns after P&R in 0.18μm technology.Because the shifter is a pivotal datapath in CPU,we optimize it in full-customdesign methodology.The circuit-level's delay is 0.94ns and delay of layout is 1.553ns.In addition,we tape it out in the form of MPW,and the result of test carries our point,and it can run at 700M Hz.In view of reuse methodology based on IP,we design it in the form of IP,such as timing and power characterization,test characterization,function's characterization,and physical characterization and so on. |
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