This application note describes how to implement a KEELOQ stand-alone programmer using a Microchip PIC16F84A microcontroller. The PIC16F84A is a FLASH microcontroller with 64 bytes of internal EEPROM that, in this design, is used to store the incremental serial number programmed into HCS encoders every time. All the other HCS con- figuration parameters are defined as constants in the FLASH program memory of the PIC16F84A. AN217 KEELOQ HCS30X, HCS200 Stand-Alone Programmer KEELOQ SIMPLE LEARNING SCHEME Author: Maurizio Fiammeni Microchip Technology Inc. (Fixed Key) This learning scheme implements the lowest level of OVERVIEW security for a KEELOQ based security system. With this method, every programmed encoder has a different This application note describes how to implement a serial number, but the same fixed Encryption Key is KEELOQ stand-alone programmer u……