A method of stabilising a laser in order to maintain the laser in SLM operation is disclosed. The connected struts may be connected by spot welding, continuous welding, or suturing, for example, or by a bridging member connected to each strut, and may be spaced along the length of the stent in a pattern to form a connective spine. When instruction codes and state signals to be executed in the slow mode match data set in the second PLA, the operation of the first PLA is stopped, and the microprocessor is controlled according to a microcode output from the second PLA.