Esterel is a imperative, synchronous language. There exists two major versions Esterel V5, which most academical tools use, and the newer Esterel V7.
Tools
Thew following tools are installed locally in /home/esterel/bin/
IDE
Compiler
- Inria Esterel compiler (esterel)
- Columbia Esterel Compiler (cec)
- KEP Kiel Esterel Processor
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)
Modules
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
Example:
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.
