The dataflow sublanguage

The dataflow sublanguage provides a convenient short-hand when designing asynchronous circuits using pipelined asynchronous circuits. The dataflow language operates exclusively on channels, and treats channels as variables to specify the dataflow computation.

chan(int) a, b, c;

dataflow {
   a + b -> c
}

This corresponds to an adder, with inputs on channels a and b and the output on channel c. There is an implicit assumption that the design is pipelined, and corresponds to the following CHP program:

*[ a?x,b?y;c!(x+y) ]

More generally, the syntax shown above corresponds to the function dataflow block. A function dataflow element receives one input token on each of its input channels, computes a function of the values received, and produces one output token with the value computed. The example above shows the function syntax. The left hand side of the arrow is a channel expression that corresponds to the function being computed, and the right hand side is the name of the channel on which the output is produced.

The split dataflow element receives a control token and a data token, and uses the value of the control token to route the data token to one of the output channels. If the control token=0, the first channel is used; if it is 1, then the next channel is used; etc. The syntax for this is shown below:

dataflow {
  {c} I -> O0, O1
}

The data input on channel I is routed to either O0 or O1, depending on the token received on input c.

The controlled merge dataflow element receives a control token, and then uses the token determine which input channel should be used to accept an input data token. This data token is routed to the output. The syntax is:

dataflow {
  {c} I0, I1 -> O
}

In this example, if a 0 is received on c, then the data token on I0 is sent to the output O.