EE382C Embedded Software Systems - Boolean Dataflow
Prof. Brian L. Evans
Firing Rules
'Firing rules' describe when an actor (node) is enabled for
execution.
Once enabled, it can be scheduled for execution either at
that point or later.
Actors in dataflow models are enabled for execution according
to the following:
- Source actors are always enabled
- Synchronous Dataflow
- Enough tokens (at least one) must be present on every input port.
- The threshold for "enough tokens" is constant (static).
- The order in reading the input ports does not matter.
- Each actor, upon execution, produces a constant (static) number
of tokens on each output port.
- Graphs can be statically scheduling.
- Boolean Dataflow firing rules
- An actor may have one or more Boolean input ports.
Boolean input ports are read first when the actor is executed.
- Other ports are either
- Conditionally read/written based on the value of a
particular Boolean input port
- Follow Synchronous dataflow firing rules
- Can build select and switch actors
- Using select and switch actors, one can define if/then/else
statements, while loops, and for loops, at the level of the graph
- Quasi-static scheduling
Updated 01/16/02.