Glue logic is a special form of digital circuitry that allows different types of logic chips or circuits to work together by acting as an interface between them. As an example, consider a chip that contains a CPU (central processing unit) and a RAM (random access memory) block. These circuits can be interfaced within the chip using glue logic, so that they work smoothly together. On printed circuit boards, glue logic can take the form of discrete ICs (integrated circuits) in their own packages. In more complicated situations, programmable logic devices (PLDs) can play the role of glue logic. Other functions of glue logic include address decoding (with older processors), interfacing to peripherals, circuits to protect against ESD (electrostatic discharge) or EMP (electromagnetic pulse) events, and the prevention of unauthorized cloning or reverse engineering, by hiding the actual function of a circuit from external observers and hackers