HCS500-ISM MICROCHIP [Microchip Technology], HCS500-ISM Datasheet - Page 2

• Manufacturer Part Number: HCS500-ISM
• Description: KEELOQ CODE HOPPING ENCODER
• Manufacturer: MICROCHIP [Microchip Technology]

HCS500
1.0
1.1
• Manufacturer’s Code – A 64-bit word, unique to
• Encoder Key – A 64-bit key, unique for each trans-
• Learn – The receiver uses information that is
The HCS encoders and decoders employ the KeeLoq
code hopping technology and a KeeLoq encryption
algorithm to achieve a high level of security. Code
hopping is a method by which the code transmitted
from the transmitter to the receiver is different every
time a button is pushed. This method, coupled with a
transmission length of 66 bits, virtually eliminates the
use of code ‘grabbing’ or code ‘scanning’.
FIGURE 1-1:
DS40153B-page 2
each manufacturer, used to produce a unique
encoder key in each transmitter.
mitter. The encoder key controls the KeeLoq
decryption algorithm and is stored in EEPROM on
the decoder device.
transmitted to derive the transmitter’s encoder key,
decrypt the discrimination value, and the synchro-
nization counter in learning mode. The encoder
key is a function of the manufacturer’s code and
the device serial number and/or seed value.
K
Key Terms
EE
Manufacturer’s
L
OQ
Code
CREATION AND STORAGE OF ENCRYPTION KEY DURING PRODUCTION
SYSTEM OVERVIEW
Serial Number or
Transmitter
Generation
Algorithm
Seed
Key
Preliminary
Encryption
1.2
The HCS encoders have a small EEPROM array which
must be loaded with several parameters before use.
The most important of these values are:
• An encoder key that is generated at the time of
• A 16-bit synchronization counter value
• A 28-bit serial number which is meant to be
The manufacturer programs the serial number for each
encoder at the time of production, while the ‘Key Gen-
eration Algorithm’ generates the encoder key (Figure 1-
1). Inputs to the key generation algorithm typically con-
sist of the encoder’s serial number and a 64-bit manu-
facturer’s code, which the manufacturer creates.
Key
production
unique for every encoder
Note:
HCS Encoder Overview
The manufacturer code is a pivotal part of
the system’s overall security. Conse-
quently, all possible precautions must be
taken and maintained for this code.
HCS500 EEPROM Array
Serial Number
Encryption Key
Sync Counter
1997 Microchip Technology Inc.
.
.
.