In this paper we consider Loosely Time-Triggered Architectures (LTTA) as a networked infrastructure for deploying discrete control. LTTA are distributed architectures in which 1/ each computing unit is triggered by its own local clock, 2/ the local clocks are not synchronized, and 3/ communication is by the following principle: each communication link acts as a shared and sustained variable that can be, at will, written by the source node and read by the destination node. The loose communication medium used can cause duplication and/or loss of events, as well as distorsion of the synchronization between events occurring at different nodes of the network. While LTT architectures possess significant advantages, their use for distributed discrete control raises serious difficulties.
Together with other authors, the authors of this paper have proposed a comprehensive design methodology ensuring the preservation of semantics, from specification to implementation over LTTA. This technique uses sophisticated token based protocols alike so-called elastic circuits recently introduced for asynchronous hardware.
In this paper we propose a completely different approach, with no flow of token, and entirely time based. Our approach relies on upsampling and suitable use of local counters. We prove the preservation of semantics, from specification to implementation on LTTA with this technique, and we study its performance.
Extended Version of Conference Paper (pdf)