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HCS473-SLQTP Datasheet(PDF) 5 Page - Microchip Technology |
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HCS473-SLQTP Datasheet(HTML) 5 Page - Microchip Technology |
5 / 68 page 2002 Microchip Technology Inc. Preliminary DS40035C-page 3 HCS473 1.0 GENERAL DESCRIPTION The HCS473 combines the patented K EELOQ code hopping technology and bi-directional transponder challenge-and-response security into a single chip solution for logical and physical access control. The three-input transponder interface allows the com- bination of three orthogonal transponder antennas, eliminating the directionality associated with traditional single antenna transponder systems. When used as a code hopping encoder, the HCS473 is well suited to keyless entry systems; vehicle and garage door access in particular. The same HCS473 can also be used as a secure bi-directional transponder for contactless authentication. These capabilities make the HCS473 ideal for combined secure access control and identification applications, dramatically reducing the cost of hybrid transmitter/transponder solutions. 1.1 System Overview 1.1.1 KEY TERMS The following is a list of key terms used throughout this data sheet. For additional information on terminology, please refer to the K EELOQ introductory Technical Brief (TB003). • AGC - Automatic Gain Control. • Anticollision - A scheme whereby transponders in the same field can be addressed individually, preventing simultaneous response to a command (Section 3.2.1.4). • Button Status - Indicates what button input(s) activated the transmission. Encompasses the 4 button status bits S3, S2, S1 and S0 (Figure 3-2). • Code Hopping - A method by which a code, viewed externally to the system, appears to change unpredictably each time it is transmitted (Section 1.2.3). • Code word - A block of data that is repeatedly transmitted upon button activation (Figure 3-2). • Crypto key - A unique and secret 64-bit number used to encrypt and decrypt data. In a symmetri- cal block cipher such as the K EELOQ algorithm, the encryption and decryption keys are equal and will therefore be referred to generally as the crypto 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 crypto key. • Device Identifier - 16-bit value used to uniquely select one of multiple transponders for communi- cation. • Encoder - A device that generates and encodes data. • Encryption Algorithm - A recipe whereby data is scrambled using a crypto key. The data can only be interpreted by the respective decryption algo- rithm using the same crypto key. • IFF - Identify Friend or Foe, a classic authentica- tion method (Section 3.2.3.3). • Learn - Learning involves the receiver calculating the transmitter’s appropriate crypto key, decrypt- ing the received hopping code and storing the serial number, synchronization counter value and crypto key in EEPROM (Section 5.1). The K EELOQ product family facilitates several learning strategies to be implemented on the decoder. The following are examples of what can be done. • Simple Learning The receiver uses a fixed crypto key, common to all components of all systems by the same manu- facturer, to decrypt the received code word’s encrypted portion. • Normal Learning The receiver uses information transmitted during normal operation to derive the crypto key and decrypt the received code word’s encrypted por- tion. • Secure Learn The transmitter is activated through a special but- ton combination to transmit a stored 60-bit seed value used to derive the transmitter’s crypto key. The receiver uses this seed value to calculate the same crypto key and decrypt the received code word’s encrypted portion. • LF - Low Frequency. For HCS473 purposes, LF refers to a typical 125 kHz frequency. • Manufacturer’s code – A unique and secret 64- bit number used to generate unique encoder crypto keys. Each encoder is programmed with a crypto key that is a function of the manufacturer’s code. Each decoder is programmed with the man- ufacturer code itself. • Proximity Activation - A method whereby an encoder automatically initiates a transmission in response to detecting an inductive field (Section 3.1.1.2). • PKE - Passive Keyless Entry. • RKE - Remote Keyless Entry. • Transmission - A data stream consisting of repeating code words. • Transcoder - Device combining unidirectional transmitter capabilities with bi-directional authenti- cation capabilities. • Transponder - A transmitter-receiver activated for transmission by reception of a predetermined signal. |
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