GENERAL DESCRIPTION
The HCS473 combines the patented KEELOQ 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 combination of three orthogonal transponder antennas, eliminating the directionality associated with traditional single antenna transponder systems.

FEATURES
Encoder Security
• Read protected 64-bit encoder key
• 69-bit transmission length
• 60-bit, read protected seed for secure learning
• Programmable 32-bit serial number
• Non-volatile 16/20-bit synchronization counter

Encoder Operation
• 2.05V to 5.5V operation
• Four switch inputs – up to 15 functions codes
• PWM or Manchester modulation
• Selectable Baud Rate (416 - 5,000 bps)
• Transmissions include button queuing information
• PLL interface

Transponder Security
• 2 read protected 64-bit Challenge/Response keys
• Two IFF encryption algorithms
• 16/32-bit Challenge/Response
• Separate Vehicle ID and Token ID
• 2 vehicles supported
• CRC on all communication

Transponder Operation
• Three sensitive transponder inputs
• Bi-directional transponder communication
• Transponder in/RF out operation
• Anticollision of multiple transponders
• Intelligent damping for high Q-factor LC-circuits
• Low battery operation
• Passive proximity activation
• 64-bit secure user EEPROM
• Fast reaction time

Peripherals
• Low Voltage Detector
• On-board RC oscillator with ±10% variation

Typical Applications
• Passive entry systems
• Automotive remote entry systems
• Automotive alarm systems
• Automotive immobilizers
• Gate and garage openers
• Electronic door locks (Home/Office/Hotel)
• Burglar alarm systems
• Proximity access control
• Passive proximity authentication