Techniques and tool for selecting compilation parameter values for compiling a first description of a circuit design, such as a register transfer language description, into a second description of the circuit design, such as a model description for implementation with an emulator are provided. A lock pin disposed on the lever engages with a lock pawl of a lock mechanism. The horizontal sensor array is installed on a floor and includes a plurality of light sensors arranged in straight lines a predetermined distance apart from each other. The first N-type, the third N-type, the first P-type, and the second P-type high doping regions are coupled to a ground end, the third P-type, the fifth P-type, the fourth N-type, and the fifth N-type high doping regions are coupled to a voltage supply end, and the second N-type and the fourth P type high doping regions are coupled to an inputoutput end. A selector operates according to an algorithm for selecting one of the memory cells.