GENERAL DESCRIPTION
The HCS412 combines patented KEELOQ code hopping technology with bi-directional transponder challenge-and-response security into a single chip solution for logical and physical access control.
When used as a code hopping encoder, the HCS412 is ideally suited to keyless entry systems; vehicle and garage door access in particular. The same HCS412 can also be used as a secure bi-directional transponder for contactless token verification. These capabilities make the HCS412 ideal for combined secure access control and identification applications, dramatically reducing the cost of hybrid transmitter/transponder solutions.

FEATURES
Security
• Programmable 64-bit encoder crypt key
• Two 64-bit IFF keys
• Keys are read protected
• 32-bit bi-directional challenge and response using one of two possible keys
• 69-bit transmission length
• 32-bit hopping code,
• 37-bit nonencrypted portion
• Programmable 28/32-bit serial number
• 60-bit, read protected seed for secure learning
• Two IFF encryption algorithms
• Delayed counter increment mechanism
• Asynchronous transponder communication
• Transmissions include button Queuing information

Operating
• 2.0V to 6.3V operation
• Three switch inputs: S2, S1, S0 – seven functions
• Battery-less bi-directional transponder capability
• Selectable baud rate and code word blanking
• Automatic code word completion
• Battery low detector
• PWM or Manchester data encoding
• Combined transmitter, transponder operation
• Anticollision of multiple transponders
• Passive proximity activation
• Device protected against reverse battery
• Intelligent damping for high Q LC-circuits
• 100 mVPP sensitive LC input

Typical Applications
• 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

Other
• Simple programming interface
• On-chip tunable RC oscillator, ± 10%
• On-chip EEPROM
• 64-bit user EEPROM in Transponder mode
• Battery-low LED indication
• Serialized Quick Turn Programming (SQTP^SM)
• 8-pin PDIP/SOIC
• RF Enable output
• ASK and FSK PLL interface option
• Built in LC input amplifier