This document presents guidelines for upgrading from the ST92F120 (0.50µm) to the ST92F124/F150/F250 (0.35µm). Microcontrollers for embedded applications are integrating more peripherals and larger memories. Shrinking the microcontroller die size is necessary to provide the right products with the right features at the right cost. The purpose of this document is to highlight the differences between the ST92F120 (0.50µm) and ST92F124/F150/F250 (0.35µm) microcontrollers and provide guidelines for upgrading the application's software and hardware.