HCS515 HCS515 KEELOQ Code Hopping Decoder FEATURES DESCRIPTION The Microchip Technology Inc. HCS515 is a code hop- Security ping decoder designed for secure Remote Keyless Encrypted storage of manufacturers code Entry (RKE) systems. The HCS515 utilizes the pat- ented code hopping system and high security learning Encrypted storage of encoder decryption keys mechanisms to make this a canned solution when used Up to seven transmitters can be learned code with the HCS encoders to implement a unidirectional hopping technology remote and access control systems. The HCS515 can Normal and secure learning mechanisms be used as a stand-alone decoder or in conjunction with a microcontroller. Operating 4.5V 5.5V operation PACKAGE TYPE Internal oscillator PDIP, SOIC Auto bit rate detection NC 1 14 NC Other NC 2 13 NC Stand-alone decoder VDD 3 12 Vss Internal EEPROM for transmitter storage Synchronous serial interface S1 RF IN 4 11 1 Kbit user EEPROM S0 5 10 S CLK 14-pin DIP/SOIC package MCLR S DAT 6 9 Typical Applications 7 8 NC NC Automotive remote entry systems Automotive alarm systems Automotive immobilizers BLOCK DIAGRAM Gate and garage openers Electronic door locks RFIN Reception Register Identity tokens Burglar alarm systems DECRYPTOR EE DAT Internal S DAT CONTROL Compatible Encoders EEPROM S CLK EE CLK S0 All encoders and transponders configured for the fol- S1 lowing setting: MCLR OSCILLATOR PWM modulation format (1/3-2/3) TE in the range from 100 s to 400 s The manufacturers code, encoder decryption keys, E Header 10 x T and synchronization information are stored in 28-bit Serial Number encrypted form in internal EEPROM. The HCS515 16-bit Synchronization counter uses the S DAT and S CLK inputs to communicate with a host controller device. Discrimination bits equal to Serial Number 8 LSbs 66- to 69-bit length code word. The HCS515 operates over a wide voltage range of 4.5V 5.5V. The decoder employs automatic bit rate detection, which allows it to compensate for wide vari- 2011 Microchip Technology Inc. DS40183E-page 1HCS515 ations in transmitter data rate. The decoder contains - Secure Learn sophisticated error checking algorithms to ensure only The transmitter is activated through a special valid codes are accepted. button combination to transmit a stored 60-bit seed value used to generate the transmitters crypt key. The receiver uses this seed value 1.0 SYSTEM OVERVIEW to derive the same crypt key and decrypt the Key Terms received code words encrypted portion. Manufacturers code A unique and secret 64- The following is a list of key terms used throughout this bit number used to generate unique encoder crypt data sheet. For additional information on KEELOQ and keys. Each encoder is programmed with a crypt Code Hopping, refer to Technical Brief 3 (TB003). key that is a function of the manufacturers code. RKE - Remote Keyless Entry Each decoder is programmed with the manufac- Button Status - Indicates what button input(s) turer code itself. activated the transmission. Encompasses the 4 button status bits S3, S2, S1 and S0 (Figure 7-2). 1.1 HCS Encoder Overview Code Hopping - A method by which a code, The HCS encoders have a small EEPROM array which viewed externally to the system, appears to must be loaded with several parameters before use. change unpredictably each time it is transmitted. The most important of these values are: Code word - A block of data that is repeatedly A crypt key that is generated at the time of pro- transmitted upon button activation (Figure 7-1). duction Transmission - A data stream consisting of A 16-bit synchronization counter value repeating code words (Figure 7-1). A 28-bit serial number which is meant to be Crypt key - A unique and secret 64-bit number unique for every encoder used to encrypt and decrypt data. In a symmetri- cal block cipher such as the KEELOQ algorithm, The manufacturer programs the serial number for each the encryption and decryption keys are equal and encoder at the time of production, while the Key Gen- will therefore be referred to generally as the crypt eration Algorithm generates the crypt key (Figure 1-1). key. Inputs to the key generation algorithm typically consist of the encoders serial number and a 64-bit manufac- Encoder - A device that generates and encodes data. turers code, which the manufacturer creates. Encryption Algorithm - A recipe whereby data is Note: The manufacturer code is a pivotal part of scrambled using a crypt key. The data can only be the systems overall security. Conse- interpreted by the respective decryption algorithm quently, all possible precautions must be using the same crypt key. taken and maintained for this code. Decoder - A device that decodes data received from an encoder. Decryption algorithm - A recipe whereby data scrambled by an encryption algorithm can be unscrambled using the same crypt key. Learn Learning involves the receiver calculating the transmitters appropriate crypt key, decrypting the received hopping code and storing the serial number, synchronization counter value and crypt key in EEPROM. The KEELOQ product family facil- itates several learning strategies to be imple- mented on the decoder. The following are examples of what can be done. - Simple Learning The receiver uses a fixed crypt key, common to all components of all systems by the same manufacturer, to decrypt the received code words encrypted portion. - Normal Learning The receiver uses information transmitted during normal operation to derive the crypt key and decrypt the received code words encrypted portion. DS40183E-page 2 2011 Microchip Technology Inc.