Petri net controller with hardware to avoid deadlocks

We have proposed a high speed Petri net sequence controller for systems described in Petri nets. Its hardware is capable of checking whether a transition is fireable or not, although we did not take deadlocks into consideration. If a controller described in the Petri net has deadlocks, the proper methods to avoid them is to redesign the Petri net of the controller. But sometimes it is difficult to change the net or insert several places to avoid deadlocks, because there are no general methods to remove them. Thus we propose here a hardware to avoid deadlocks without changing the Petri net graph. The hardware unit inside the Petri net controller detects unsafe markings leading to deadlocks and prevents the current transition from being fired. The unit consists of three memory tables and some logical units to detect the matching of a current marking with those in the tables. It requests one memory cycle to check one only state. This idea can be used to avoid the undesired marking of the controlled object