HCS365 HCS365 KEELOQ Code Hopping Encoder FEATURES PACKAGE TYPES PDIP, SOIC Security S0 Two programmable 32-bit serial numbers 8 VDD 1 Two programmable 64-bit crypt keys S1 LED 7 2 Two programmable 60-bit seed values Each transmission is unique S2 6 DATA 3 67/69-bit transmission code length S3/SHIFT/ Vss 4 5 32-bit hopping code RFEN Crypt keys are read protected HCS365 BLOCK DIAGRAM Operating Oscillator Power 2.05-5.5V operation latching and Controller RESET circuit Four button inputs switching 15 functions available LED LED driver Four selectable baud rates Selectable minimum code word completion Battery low signal transmitted to receiver EEPROM Encoder Nonvolatile synchronization data DATA PWM, VPWM, PPM, and Manchester modulation 32-bit SHIFT register Button queue information transmitted Dual Encoder functionality VSS Button input port VDD Other S3/SHIFT S2 S S 1 0 On-chip EEPROM RFEN On-chip tuned oscillator (10% over voltage and temperature) GENERAL DESCRIPTION Button inputs have internal pull-down resistors The HCS365 is a code hopping encoder designed for LED output secure Remote Keyless Entry (RKE) and secure PLL control for ASK and FSK remote control systems. The HCS365 utilizes the KEELOQ code hopping technology, which incorpo- Low external component count rates high security, a small package outline, and low Typical Applications cost to make this device a perfect solution for unidirec- tional authentication systems and access control sys- The HCS365 is ideal for Remote Keyless Entry (RKE) tems. applications. These applications include: The HCS365 combines a hopping code generated by a Automotive RKE systems nonlinear encryption algorithm, a serial number, and Automotive alarm systems status bits to create a secure transmission code. The Automotive immobilizers length of the transmission eliminates the threat of code scanning and code grabbing access techniques. Gate and garage door openers Identity tokens Burglar alarm systems 2011 Microchip Technology Inc. DS41109E-page 1HCS365 The crypt key, serial number, and configuration data - Simple Learning are stored in an EEPROM array which is not accessible The receiver uses a fixed crypt key. The crypt via any external connection. The EEPROM data is pro- key is common to every component used by grammable but read protected. The data can be veri- the same manufacturer. fied only after an automatic erase and programming - Normal Learning operation. This protects against attempts to gain The receiver derives a crypt key from the access to keys or manipulate synchronization values. encoder serial number. Every transmitter has In addition, the HCS365 supports a dual encoder. This a unique crypt key. allows two manufacturers to use the same device with- - Secure Learning out having to use the same manufacturers code in The receiver derives a crypt key from the each of the encoders. The HCS365 provides an easy encoder seed value. Every encoder has a to use serial interface for programming the necessary unique seed value that is only transmitted by keys, system parameters, and configuration data. a special button combination. Manufacturers Code A unique and secret 64- 1.0 SYSTEM OVERVIEW bit number used to derive crypt keys. Each encoder is programmed with a crypt key that is a Key Terms function of the manufacturers code. Each The following is a list of key terms used throughout this decoder is programmed with the manufacturer data sheet. For additional information on KEELOQ and code itself. code hopping, refer to Technical Brief (TB003). The HCS365 code hopping encoder is designed specif- RKE - Remote Keyless Entry ically for keyless entry systems. In particular, typical Button Status - Indicates what button input(s) applications include vehicles and home garage door openers. The encoder portion of a keyless entry sys- activated the transmission. Encompasses the 4 tem is integrated into a transmitter carried by the user. button status bits S3, S2, S1 and S0 (Figure 3-2). The transmitter is operated to gain access to a vehicle Code Hopping - A method by which a code, or restricted area. The HCS365 is meant to be a cost- viewed externally to the system, appears to effective yet secure solution to such systems requiring change unpredictably each time it is transmitted. very few external components (Figure 2-1). Code Word - A block of data that is repeatedly transmitted upon button activation (Figure 3-2). Most low end keyless entry transmitters are given a fixed identification code that is transmitted every time a Transmission - A data stream consisting of button is pushed. The number of unique identification repeating code words (Figure 4-1). codes in a low end system is usually a relatively small Crypt Key - A unique and secret 64-bit number number. These shortcomings provide an opportunity used to encrypt and decrypt data. In a symmetri- for a sophisticated thief to create a device that grabs cal block cipher such as the KEELOQ algorithm, a transmission and retransmits it later or a device that the encryption and decryption keys are equal and quickly scans all possible identification codes until the will therefore be referred to generally as the crypt correct one is found. key. The HCS365, on the other hand, employs the KEELOQ Encoder - A device that generates and encodes code hopping technology coupled with a transmission data. length of 67 bits to virtually eliminate the use of code Encryption Algorithm - A recipe whereby data is grabbing or code scanning. The high security level of scrambled using a crypt key. The data can only be the HCS365 is based on the patented KEELOQ technol- interpreted by the respective decryption algorithm ogy. A block cipher based on a block length of 32 bits using the same crypt key. and a key length of 64 bits is used. The algorithm Decoder - A device that decodes data received obscures the information in such a way that if a single from an encoder (i.e., HCS5XX). hopping code data bit changes (before encryption), sta- Decryption Algorithm - A recipe whereby data tistically more than 50% of the encrypted data bits will scrambled by an encryption algorithm can be change. 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. DS41109E-page 2 2011 Microchip Technology Inc.