HCS500 HCS500 KEELOQ Code Hopping Decoder FEATURES DESCRIPTION The Microchip Technology Inc. HCS500 is a code hop- Security ping decoder designed for secure Remote Keyless Encrypted storage of manufacturers code Entry (RKE) systems. The HCS500 utilizes the pat- ented KEELOQ code hopping system and high security Encrypted storage of crypt keys learning mechanisms to make this a canned solution Up to seven transmitters can be learned when used with the HCS encoders to implement a uni- KEELOQ code hopping technology directional remote and access control systems. The Normal and Secure learning mechanisms HCS500 can be used as a stand-alone decoder or in conjunction with a microcontroller. Operating PACKAGE TYPE 3.0V5.5V operation Internal oscillator PDIP, SOIC Auto bit rate detection VDD 1 8 VSS Other EE CLK 2 7 RFIN Stand-alone decoder chipset EE DAT 3 6 S CLK External EEPROM for transmitter storage MCLR 4 5 S DAT Synchronous serial interface 1 Kbit user EEPROM 8-pin DIP/SOIC package BLOCK DIAGRAM Typical Applications RFIN Automotive remote entry systems Reception Register Automotive alarm systems DECRYPTOR Automotive immobilizers EE DAT Gate and garage openers External S DAT CONTROL EEPROM S CLK EE CLK Electronic door locks Identity tokens MCLR Burglar alarm systems OSCILLATOR Compatible Encoders All KEELOQ encoders and transponders configured for The manufacturers code, crypt keys, and synchroniza- the following setting: tion information are stored in encrypted form in external EEPROM. The HCS500 uses the S DAT and S CLK PWM modulation format (1/3-2/3) inputs to communicate with a host controller device. TE in the range from 100us to 400us The HCS500 operates over a wide voltage range of 10 x TE Header 3.0 volts to 5.5 volts. The decoder employs automatic 28-bit Serial Number bit-rate detection, which allows it to compensate for 16-bit Synchronization counter wide variations in transmitter data rate. The decoder Discrimination bits equal to Serial Number 8 LSbs contains sophisticated error checking algorithms to 66- to 69-bit length code word. ensure only valid codes are accepted. 2002 Microchip Technology Inc. DS40153C-page 1HCS500 to derive the same crypt key and decrypt the 1.0 SYSTEM OVERVIEW received code words encrypted portion. Key Terms 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. Each decoder is programmed with the manufac- RKE - Remote Keyless Entry turer code itself. Button Status - Indicates what button input(s) activated the transmission. Encompasses the 4 1.1 HCS Encoder Overview button status bits S3, S2, S1 and S0 (Figure 7-2). The HCS encoders have a small EEPROM array which Code Hopping - A method by which a code, must be loaded with several parameters before use. viewed externally to the system, appears to The most important of these values are: change unpredictably each time it is transmitted. 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- The manufacturer programs the serial number for each cal block cipher such as the KEELOQ algorithm, encoder at the time of production, while the Key Gen- the encryption and decryption keys are equal and eration Algorithm generates the crypt key (Figure 1-1). will therefore be referred to generally as the crypt Inputs to the key generation algorithm typically consist key. of the encoders serial number and a 64-bit manufac- Encoder - A device that generates and encodes turers code, which the manufacturer creates. data. Note: The manufacturer code is a pivotal part of Encryption Algorithm - A recipe whereby data is the systems overall security. Conse- scrambled using a crypt key. The data can only be quently, all possible precautions must be interpreted by the respective decryption algorithm taken and maintained for this code. using the same crypt key. 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. - Secure Learn The transmitter is activated through a special button combination to transmit a stored 60-bit seed value used to generate the transmitters crypt key. The receiver uses this seed value DS40153C-page 2 2002 Microchip Technology Inc.