HCS473_13 datasheet(3/68 Pages) MICROCHIP

3 / 68 page

 2000-2013 Microchip Technology Inc.

Preliminary

DS40035D-page 3

HCS473

1.0

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 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 KEELOQ 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 KEELOQ 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

KEELOQ 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.

HCS473 Datasheet(PDF) 3 Page - Microchip Technology

HCS473 Datasheet(HTML) 3 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68

Datasheet Download

Link URL