低功率多工樹之輸入選擇編碼演算法

Abstract

隨著攜帶式設備的出現，功率消耗變成在VLSI設計上重要的考量之一。在VLSI設計中，多工器是基本且常用的元件。ㄧ般而言，標準元件庫只提供2對1多工器和4對1多工器。不同大小的多工器在不同的設計裡都可使用到，因此通常多對1多工器會被拆解為用2對1多工器組成的樹狀實現。交換頻率(switching activity)是影響功率消耗重要的因素之一。在此論文裡，我們針對在多工器樹裡面的每一個2對1多工器的交換頻率做最小化的處理。我們利用輸入訊號變成邏輯1的機率來分析在多工樹裡面每一個2對1多工器的交換頻率。我們解決的以下的問題: 給予輸入信號變成邏輯1的機率和輸入信號被選到的機率，我們提出的演算法有效率地給予每個輸入資料訊號輸入選擇編碼,同時依照每個輸入資料訊號輸入選擇編碼產生了最小化功率消耗的多工樹。最後，實驗結果顯示我們提出的演算法在64對1多工器的情況下求出的功率消耗比平均功率消耗減少了24%。

With the advent of portable devices, power consumption becomes one of most important considerations in the VLSI designs. Multiplexer (MUX) is a basic component that is commonly used in VLSI designs. In general, only 2-to-1 and 4-to-1 MUX are available in the standard cell library. Any size of MUX could be used in various design blocks. Usually, an n-to-1 MUX is decomposed as an equivalent tree of 2-to-1 MUXes. The switch activity is an important factor of power consumption. In this thesis, we focus on the minimization of the switch activity for each 2-to-1 MUXes in the MUX tree. We utilize the on probabilities of input signals to analyze the switching activity of 2-to-1 MUXes in a MUX tree. We solve the following problem: Given the on probabilities and the selection probabilities of input data signals, our proposed algorithm efficiently assigns each input selection encoding for input data signals. According to each input selection encoding of input data signals, a minimum power MUX tree is generated. Finally, the experimental results reveal that our proposed algorithm reduces up to 24% power dissipation for 64-to-1 MUX when compared to average power dissipation.