Compositionality of Statically Scheduled IP

Abstract

Timing Closure in presence of long global wire interconnects is one of the main current issues in System-on-Chip design. One proposed solution to the Timing Closure problem is Latency-Insensitive Design (LID) [Luca Carloni, Kenneth McMillan, and Alberto Sangiovanni-Vincentelli. Theory of latency-insensitive design. IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, vol. 20(no. 9):pp. 1059–1076, 2001; Mario R. Casu and Luca Macchiarulo. A new approach to latency insensitive design. In DAC'04: Proceedings of the 41st annual conference on Design automation, pages 576–581, New York, NY, USA, 2004. ACM Press].It was noticed in [Mario R. Casu and Luca Macchiarulo. A new approach to latency insensitive design. In DAC '04: Proceedings of the 41st annual conference on Design automation, pages 576–581, New York, NY, USA, 2004. ACM Press] that, in many cases, the dynamically scheduled synchronisations introduced by latency-insensitive protocols could be computed off-line as a static periodic schedule. We showed in [Julien Boucaron, Jean-Vivien Millo, and Robert De Simone. Latency-insensitive design and central repetitive scheduling. In Formal Methods and Models for Co-Design, 2006. MEMOCODE'06. Proceedings. Fourth ACM and IEEE International Conference on, pages 175–183, Piscataway, NJ, USA, 2006. IEEE Press; Julien Boucaron, Jean-Vivien Millo, and Robert De Simone. Formal methods of scheduling for latency-insensitive designs. EURASIP journal on embedded system, 2007 (not yet published)] how this schedule could then be used to further optimize the protocol resources when they are found redundant. The purpose of the present paper is to study how the larger blocks, obtained as synchronous components interconnected by LID protocols optimized by static schedule informations, can be again made to operate with an environment that provides also I/O connections at its own (synchronous or GALS) rate.We also consider the case of multirate SoC, using results from SDF (Synchronous DataFlow) theory [Edward A. Lee and David G. Messerschmitt. Synchronous data flow. Proceeding of the IEEE, vol. 75(no. 9):pp. 1235–1245, 1987].