Design of Time-Deterministic Communica- tion in a Computer System for Embedded Real-Time Applications

A time-deterministic inter-module communication architecture for embedded computer systems is presented. The architecture is general in the sense that a bit-parallel word of any size is transferred from/to the processing unit via the communication unit on/from the shared medium. To get a time-deterministic communication the communication is executed cyclically and the resources (time slots and wavelengths) are statically allocated in the design phase. The shared communication medium is implemented using an optical technology. The “building block” is an all-optical star. To build large networks the shared medium is partitioned into subnetworks (clusters); then a spatial overlapping of communication resources and low splitting losses in each subnetwork are achieved. To utilize the high bandwidth of the fibre, wavelength division multiplexing (WDM) is used. By using WDM several parallel communication cycles are created in each subnetwork, also a manyto-many communication between modules is achieved. Each communication cycle is further divided into a number of time slots (TDM). To get a simpler scheme when allocating time slots the cycles in each module are skewed according to their physical length to the centre of the star. New concepts of a “discrete tunable” transmitter and receiver are also proposed. The performance of the communication architecture is several Gb/s per module and several Tb/s for the whole network.