now only correct chart can be created in SFC Viewer
if user trying to connect incompatible blocks (by IEC 61131-3 standard), wire highlight will become red
int CheckRetainBuffer(void){ return 1;}void ValidateRetainBuffer(void){}void InValidateRetainBuffer(void){}void Retain(unsigned int offset, unsigned int count, void *p){}void Remind(unsigned int offset, unsigned int count, void *p){}