The TWR-K20D72M is a tower system module for Kinetis MK20DX256VLL7 microcontroller. It is a low cost evaluation, demonstration and development board, which features the Kinetis K20 72MHz low power microcontroller. These devices are based on the ARM Cortex-M4 architecture with USB 2.0 full speed OTG controller. The TWR-K20D72M microcontroller module can operate in standalone mode or as part of the tower system, a modular development platform that enables rapid prototyping and tool reuse through reconfigurable hardware. This tower system module features two expansion card edge connectors that interface to elevator boards in a tower system, the primary and secondary elevator connectors. In standalone operation, the main power source for the TWR-K20D72M is derived from the 5.0V input from either the USB mini B connector. When installed into a tower system, the TWR-K20D72M can be powered from either an onboard source or from another source in the assembled tower system.