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SystemC Signals

Signals have a current value and a next value. Assigns are to the next value whereas reads use the current value. The next value is copied to the current value in a commit cycle when there are no futher events of the current tnow on the event queue.

For faster system modelling, we do not want to enter EDS kernel for every change of every net: so is it possible to pass larger objects around, or even send threads between components, like S/W does ?

It is possible to put any datatype inside a signal and route that signal between components (provided the datatype can be checked for equality to see if current and nex are different and so on). So yes, using this approach, a higher-level model is possible, because a complete Ethernet frame or other large item can be delivered as a single event, rather than having to step though the cycle-by-cycle operation of a serial hardware implementation.

SystemC 2.0 enabled threads to be passed along the channels, breaking away from just using signals. This enables the transactional calls introduced in LG4 to be passed along structures that were previously EDS nets carrying logic values.

(C) 2008-10, DJ Greaves, University of Cambridge, Computer Laboratory.