KEELOQ® Simple Code Hopping Decoder

This application note fully describes the working of a code hopping decoder implemented on a Microchip PIC16C54 microcontroller. The PIC16C54 is smaller than the PIC16C56 used in the normal decoder (AN642) or the secure learn decoder (AN652). A sim-plified learning scheme with all encoders sharing a common key and a simplified counter synchronization scheme has been used to reduce the code space requirements. The use of a common key reduces the security of the system. The simple decoder can learn up to 15 encoders. This application note describes the various KEELOQ code hopping encoders that can be used with the decoder, the decoder hardware, and the various software modules comprising the system. The software can be used to implement a stand alone decoder or integrated with full function security systems. The decoder supports the Microchip HCS200, HCS300, HCS301, HCS360, HCS361 and HCS410 KEELOQ Code Hopping Encoders.