HCS362 HCS362 HCS362 KEELOQ Code Hopping Encoder FEATURES PACKAGE TYPES Security PDIP, SOIC Programmable 28/32-bit serial number S0 VDD 1 8 Two programmable 64-bit encryption keys LED/SHIFT 2 S1 7 Programmable 60-bit seed Each transmission is unique DATA 3 S2 6 69-bit transmission code length VSS S3/RFEN 4 32-bit hopping code 5 37-bit fixed code (28/32-bit serial number, 4/0-bit function code, 1-bit status, 2-bit CRC/time, 2-bit queue) TSSOP Encryption keys are read protected S2 S1 1 8 S3/RFEN 2 7 S0 Operation VSS 3 6 VDD 4 5 DATA LED/SHIFT 2.0V 6.3V operation Four button inputs 15 functions available HCS362 BLOCK DIAGRAM Selectable baud rates and code word blanking Oscillator Programmable minimum code word completion Power Latching RESET Circuit Battery low signal transmitted to receiver with and Controller LED Switching programmable threshold LED Driver RFEN Non-volatile synchronization data PLL Driver PWM and Manchester modulation EEPROM Other Encoder RF Enable output PLL interface DATA 32-bit Shift Register Easy to use programming interface On-chip EEPROM VSS SHIFT On-chip tunable oscillator and timing components Button Input Port VDD Button inputs have internal pull-down resistors S3 S2 S1 S0 Current limiting on LED output Minimum component count Typical Applications Enhanced Features Over HCS300 The HCS362 is ideal for Remote Keyless Entry (RKE) 60-bit seed vs. 32-bit seed applications. These applications include: 2-bit CRC for error detection Automotive RKE systems 28/32-bit serial number select Automotive alarm systems Tunable oscillator (+/10% over specified voltage Automotive immobilizers ranges) Gate and garage door openers Time bits option Identity tokens Queue bits Burglar alarm systems TSSOP package Programmable Time-out and Guard Time 2011 Microchip Technology Inc. DS40189E-page 1HCS362 Decoder - A device that decodes data received GENERAL DESCRIPTION from an encoder. The HCS362 is a code hopping encoder designed for Decryption algorithm - A recipe whereby data secure Remote Keyless Entry (RKE) systems. The scrambled by an encryption algorithm can be EELOQ code hopping technol- HCS362 utilizes the K unscrambled using the same crypt key. ogy, which incorporates high security, a small package Learn Learning involves the receiver calculating outline and low cost, to make this device a perfect the transmitters appropriate crypt key, decrypting solution for unidirectional remote keyless entry sys- the received hopping code and storing the serial tems and access control systems. number, synchronization counter value and crypt The HCS362 combines a 32-bit hopping code key in EEPROM. The KEELOQ product family facil- generated by a nonlinear encryption algorithm, with a itates several learning strategies to be imple- 28/32-bit serial number and 9/5 status bits to create a mented on the decoder. The following are 69-bit transmission stream. The length of the transmis- examples of what can be done. sion eliminates the threat of code scanning. The code - Simple Learning hopping mechanism makes each transmission unique, The receiver uses a fixed crypt key, common thus rendering code capture and resend (code grab- to all components of all systems by the same bing) schemes useless. manufacturer, to decrypt the received code The crypt key, serial number and configuration data are words encrypted portion. stored in an EEPROM array which is not accessible via - Normal Learning any external connection. The EEPROM data is pro- The receiver uses information transmitted grammable but read protected. The data can be veri- during normal operation to derive the crypt fied only after an automatic erase and programming key and decrypt the received code words operation. This protects against attempts to gain encrypted portion. access to keys or manipulate synchronization values. - Secure Learn The HCS362 provides an easy to use serial interface The transmitter is activated through a special for programming the necessary keys, system parame- button combination to transmit a stored 60-bit ters and configuration data. seed value used to generate the transmitters crypt key. The receiver uses this seed value 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 EELOQ and data sheet. For additional information on K 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 The HCS362 code hopping encoder is designed specif- ically for keyless entry systems primarily vehicles and button status bits S3, S2, S1 and S0 (Figure 3-2). home garage door openers. The encoder portion of a Code Hopping - A method by which a code, keyless entry system is integrated into a transmitter, viewed externally to the system, appears to carried by the user and operated to gain access to a change unpredictably each time it is transmitted. vehicle or restricted area. The HCS362 is meant to be Code word - A block of data that is repeatedly a cost-effective yet secure solution to such systems, transmitted upon button activation (Figure 3-2). requiring very few external components (Figure 2-1). Transmission - A data stream consisting of Most low-end keyless entry transmitters are given a repeating code words (Figure 8-1). fixed identification code that is transmitted every time a Crypt key - A unique and secret 64-bit number button is pushed. The number of unique identification used to encrypt and decrypt data. In a symmetri- codes in a low-end system is usually a relatively small cal block cipher such as the KEELOQ algorithm, number. These shortcomings provide an opportunity the encryption and decryption keys are equal and for a sophisticated thief to create a device that grabs will therefore be referred to generally as the crypt a transmission and retransmits it later, or a device that key. quickly scans all possible identification codes until the Encoder - A device that generates and encodes correct one is found. data. The HCS362, on the other hand, employs the KEELOQ Encryption Algorithm - A recipe whereby data is code hopping technology coupled with a transmission scrambled using a crypt key. The data can only be length of 66 bits to virtually eliminate the use of code interpreted by the respective decryption algorithm grabbing or code scanning. The high security level of using the same crypt key. DS40189E-page 2 2011 Microchip Technology Inc.