AN652

AN652 Code Hopping Decoder Using Secure Learn Author: Steven Dawson Standard Microcontroller and ASSP Division KEY FEATURES Stand alone decoder Compatible with Microchip HCS200, HCS300, HCS301, HCS360, and HCS361 encoders Automatic bit rate detection Automatic encoder type detection Four function outputs Six learnable transmitters RC Oscillator OVERVIEW This application note fully describes the working of a code hopping decoder implemented on a Microchip PIC16C56 microcontroller. This decoder uses the secure learn (seed-based) method of learning new transmitters. 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 integrate with full function security systems. The decoder supports the Microchip HCS200, HCS300, HCS301, HCS360, and HCS361 KEELOQ code hopping encoders. FIGURE 1: LEARN INIT LEARN IND Vcc MCLR GND S0 S1 S2 S3 PIC16C56 KEELOQ DECODER 1 2 3 PIC16C56 Secure Learn Decoder 4 5 6 7 8 9 18 17 16 15 14 13 12 11 10 RFIN NC OSC OUT OSC IN Vcc BUT LRNT EE CS EE CK EE DIO THE INFORMATION CONTAINED IN THIS DOCUMENT IS PROPRIETARY AND CONFIDENTIAL INFORMATION OF MICROCHIP TECHNOLOGY INC. THEREFORE, ALL PARTIES ARE REQUIRED TO ENTER INTO A NONDISCLOSURE AGREEMENT BEFORE RECEIVING THIS DOCUMENT. KEELOQ is a registered trademark of Microchip Technology Inc. © 1996 Mi...