The Esterel v5 21 System Manual - Courses

2.3. CONTROLLING CODE GENERATION 17
module Cyclic1:
output X, Y;
present X then emit Y end;
pause;
present Y then emit X end
end module
module Cyclic2:
input I;
output X, Y;
present I then
present X then emit Y end
else
present Y then emit X end
end present
end module
In both programs, there is a static instantaneous dependency from X to Y
due to “present X then emit Y” and a reverse static instantaneous dependency
from Y to X due to “present Y then emit X”. In Cyclic1, because
of the “pause” statement, the potential cycle is not an actual cycle since the
dependencies are not active at the same instant. In Cyclic2, the potential
cycle is not an actual cycle since the first dependency is meaningful only if
I is present while the second dependency is meaningful only if I is absent.
(Try esterel -cycles to visualize the static cycles). These facts cannot be
discovered by simple equation sorting. They require the much more elaborate
constructive causality analysis performed by the sccausal processor
when option -causal is set. Beware: the -causal option can be expensive
in compiling time and space. More details on code generation from cyclic
programs can be found in Chapter 8.
The -L target language definition option can be used to change the target
language. The L letter is followed by a language name. For example,
esterel -Ldebug foo.strl
esterel -causal -Ldebug cycle.strl
generate a readable code using sscdebug instead of sscc. For Pure Esterel
programs, one can use the -Lblif option to generate a blif hardware
circuit:
esterel -Lblif foo.strl