Implementation of a Low-Power FPGA Based on Synchronous/Asynchronous Hybrid Architecture

Shota ISHIHARA  Ryoto TSUCHIYA  Yoshiya KOMATSU  Masanori HARIYAMA  Michitaka KAMEYAMA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E94-C   No.10   pp.1669-1679
Publication Date: 2011/10/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E94.C.1669
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Electronic Circuits
Keyword: 
mixed synchronous/asynchronous design,  reconfigurable VLSI,  four-phase dual-rail encoding,  self-timed architecture,  GALS (Globally Asynchronous Locally Synchronous),  

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Summary: 
This paper presents a low-power FPGA based on mixed synchronous/asynchronous design. The proposed FPGA consists of several sections which consist of logic blocks, and each section can be used as either a synchronous circuit or an asynchronous circuit according to its workload. An asynchronous circuit is power-efficient for a low-workload section since it does not require the clock tree which always consumes the power. On the other hand, a synchronous circuit is power-efficient for a high-workload section because of its simple hardware. The major consideration is designing an area-efficient synchronous/asynchronous hybrid logic block. This is because the hardware amount of the asynchronous circuit is about double that of the synchronous circuit, and the typical implementation wastes half of the hardware in synchronous mode. To solve this problem, we propose a hybrid logic block that can be used as either a single asynchronous logic block or two synchronous logic blocks. The proposed FPGA is fabricated using a 65-nm CMOS process. When the workload of a section is below 22%, asynchronous mode is more power-efficient than synchronous mode. Otherwise synchronous mode is more power-efficient.