Esterel is a imperative, synchronous language. There exists two major versions Esterel V5, which most academical tools use, and the newer Esterel V7.


Thew following tools are installed locally in /home/esterel/bin/



Managing Traces

Traces of Esterel programs are usually given as esi ? or eso ? files. The following tools to work with esi and eso files are installed in /home/esterel/bin

  • eso2esi: removes all outputs from an eso file
  • esoDiff: compares two eso files and gives the first trace they differ in, if they do
  • esoPrint: pretty printer for eso Files

Additional tools

  • v5tov7 is a script based on the CEC to convert Esterel V5 programs into Esterel V7

Semantic differences between v5 / v7 (incomplete)


In the Esterel v5, the semantic of the instantiation of modules is simply a textual copy and paste, with renaming of signals. In Esterel v7, the behavior is more subtle.

  • emitting inputs across modules does not work in v7: define that input as output with the same name


main module main_mod:

input i, env_i; output o; run sub;

loop await i do

emit o

end await end loop;

end module

module sub:

input i,env_i; output i; change input i to output and it works fine sustain {

i <= env_i


end module

*Similar, reading outputs does not work:

main module M:

input I; output O:int init 0; signal S: int init 0 in

every I do

run Count[S/C]; emit O(?S);

end every

end signal

end module

module Count:

output C : int; emit C(sat<32>(pre(?C)+1));

end module

The global initialization does not reach C, hence it is not initialized when I occurs for the first time. Hence C is a local signal, when it is read, but it is a global signal when it is written. So you have to declare C as inputoutput;

New statements

  • Esterel v7 allows the use of expressions as conditions for strong aborts, but this is somehow tricky. The expression is evaluated before the abort body is executed. When a variable is changed inside the body, making the abort condition true, no abort takes place, not even a weak one.

main module T:

input I; output O : int;

var v : int in

v:=0; abort

every I do v:=sat<32>(v+1); end

when v=3; emit O(v);

end var

end module

The O will be present in the instant after the third I occurred.

  • It is now possible to emit signals in the next instant. Unfortunately, this will be silently omitted, if the module terminates in the current instant: main module M:

signal S in run sub[S/O]; await immediate S; halt; control never reaches this point. end signal

end module

module sub:

output O : reg; emit next O; pause;

end module

If possible, you can simply add a pause at the end of the module, but of course this can change the overall behavior of the model.

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