Hi all, The documentation for RTX51 Tiny says that "standart c51 functions must not be called simultaneously". The explanation is simple: standart functions uses fixed locations for parameters. Documentation also advices to use reentrant functions instead, but it also says that task switching should also be disabled with reentrant functions. But, what about the os_xxx() functions. Are they reentrant? If they are why do not we disable task switching when calling os_wait() ? What kind of functions (reentrant/normal) do you use with RTX51 tiny? regards,