© 1996 Microchip Technology Inc.

Preliminary

DS21143A-page 1

FEATURES

Security

• Programmable 28-bit serial number

• Programmable 64-bit encryption key

• Each transmission is unique

• 66-bit transmission code length

• 32-bit hopping code

• 34-bit fixed code (28-bit serial number,

4-bit button code, 2-bit status)

• Encryption keys are read protected

Operating

• 3.5V - 13.0V operation

• Four button inputs

- 15 functions available

• Selectable baud rate

• Automatic code word completion

• Battery low signal transmitted to receiver

• Battery low indication on LED

• Non-volatile synchronization data

Other

• Functionally identical to HCS300

• Easy to use programming interface

• On-chip EEPROM

• On-chip oscillator and timing components

• Button inputs have internal pulldown resistors

• Current limiting on LED output

• Low external component cost

Typical Applications

The HCS301 is ideal for Remote Keyless Entry (RKE)

applications. These applications include:

• Automotive RKE systems

• Automotive alarm systems

• Automotive immobilizers

• Gate and garage door openers

• Identity tokens

• Burglar alarm systems

DESCRIPTION

The HCS301, from Microchip Technology Inc., is a code

hopping encoder designed for secure Remote Keyless

code hopping technology, which incorporates high secu-

rity, a small package outline, and low cost, to make this

device a perfect solution for unidirectional remote key-

less entry systems and access control systems.

PACKAGE TYPES

HCS301 BLOCK DIAGRAM

The HCS301 combines a 32-bit hopping code

generated by a non-linear encryption algorithm, with a

28-bit serial number and six status bits to create a

66-bit

transmission

stream. The

length

of

the

transmission eliminates the threat of code scanning

and the code hopping mechanism makes each

transmission unique, thus rendering code capture and

resend (code grabbing) schemes useless.

The encryption key, serial number, and configuration

data are stored in EEPROM which is not accessible via

any external connection. This makes the HCS301 a

very secure unit. The HCS301 provides an easy to use

serial interface for programming the necessary security

keys, system parameters, and configuration data.

The encryption keys and code combinations are pro-

grammable but read-protected. The keys can only be

verified after an automatic erase and programming

operation. This protects against attempts to gain

access to keys and manipulate synchronization values.

1

2

3

4

8

7

6

5

S0

S1

S2

S3

LED

PWM

PDIP, SOIC

Oscillator

Reset circuit

LED driver

Controller

Power

latching

and

switching

Button input port

32-bit shift register

Encoder

EEPROM

PWM

LED

HCS301

KeeLoq is a registered trademark of Microchip Technology Inc.

*Code hopping encoder patents issued for Europe, U. S. A., and R. S. A.

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