Large scale integration (LSI) technology can also be used to implement sequential systems. One approach consists in using ROM circuits for the combinational logic block and latches or a counter as memory elements. This simple ROM-based µcontrollers, later evolved into what we know today as µprocessors, by integrating different complementary circuits.
Another approach, derived from programmable logic devices (PLDs), is based on Field Programmable Gate Arrays (FPGA). These LSI circuits include several logic cells with each cell containing simple combinational and sequential elements the cells can be interconnected in different ways to implement very complex designs in a single chip, which can also be reconfigured at any time.