考慮耦合電容以降低功率消耗的資料傳輸編解碼之有效方法

Abstract

由於製程的進步，電路愈益精密，匯流排的長度也越來越長。而在匯流排中，線路間的距離也越來越短，其間所產生的寄生電容值則增大，使得其每次的充放電事件消耗了更多的電能。因此，如何同時降低自生電容與耦合電容在匯流排中所消耗的電能，成為一個很重要的課題。我們在本篇論文中，提出一個方法amount-driven encoding method (ADEM)，針對on-chip的資料匯流排所消耗的電能進行改善，藉由整合資料編碼與Spacing的技術來達到此目標。我們將匯流排中的線路視為兩兩成對的相鄰線路，且沒有交集。再利用Spacing的技術以減小此成對的線路間所產生的耦合電容值，並對此成對之線路中的資料以四種編碼方式進行編碼，同時降低在此成對線路中自生電容與耦合電容所發生的充放電事件次數，進而達到低功率消耗的目標。我們模擬常見的多媒體檔案在匯流排中傳輸所消耗的電能，結果顯示ADEM在低功率消耗的效能上達到了25%的改進。相較於過去的相關研究，除了節省了更多的耗能，我們在電路複雜度與時間延遲方面，也有較好的表現。

As technology trends advancing, the increased bus length and the narrower geometrical proximity of adjacent bus lines form non-negligible coupling capacitances between two adjacent bus lines. Therefore, more power dissipation is caused by charge and discharge of the coupling capacitances. In this case, the effect of line-to-ground and coupling capacitances plays an important role for low-power bus system. In this thesis, we propose an integrated method, named amount-driven encoding method (ADEM), which minimizes the power dissipation of on-chip data buses through combining bus encoding and Spacing mechanisms. In our bus model, the bus lines are considered as the constitution of several adjacent pairs without intersection. Spacing mechanism is applied to decrease the values of coupling capacitances between pairs. For coupling capacitances between two adjacent lines within a pair, we reduce the charge and discharge times of them by applying four encoding methods in each bus cycle. Our method saves more than 25% of bus power on average compared to the un-encoded cases by transferring a large set of common used multimedia files on the bus. Comparing to previous work, ADEM saves more power effectively with a little overhead of circuit complexity and delay time.